diff --git a/simple-translate/manifest.json b/simple-translate/manifest.json
index 3326e66..7c0317c 100644
--- a/simple-translate/manifest.json
+++ b/simple-translate/manifest.json
@@ -50,7 +50,7 @@
         {
             "matches": ["http://*/*", "https://*/*", "<all_urls>"],
             "css": ["simple-translate.css"],
-            "js": ["Settings.js", "simple-translate.js"]
+            "js": ["Settings.js", "Translate.js", "simple-translate.js"]
         }
     ]
 }
diff --git a/simple-translate/popup/popup.css b/simple-translate/popup/popup.css
index ef649c3..6f86c73 100644
--- a/simple-translate/popup/popup.css
+++ b/simple-translate/popup/popup.css
@@ -97,6 +97,10 @@ hr {
 
 #target .candidate {
     color: var(--sub-text);
+    margin-top:1em;
+}
+#target .candidate:empty {
+    margin-top:0;
 }
 
 #footer {
diff --git a/simple-translate/popup/popup.html b/simple-translate/popup/popup.html
index 144fcfd..8978ad2 100644
--- a/simple-translate/popup/popup.html
+++ b/simple-translate/popup/popup.html
@@ -30,6 +30,7 @@
     </div>
 
     <script src="../Settings.js"></script>
+    <script src="../translate.js"></script>
     <script src="popup.js"></script>
 </body>
 
diff --git a/simple-translate/popup/popup.js b/simple-translate/popup/popup.js
index 7d41d58..c1be2b6 100644
--- a/simple-translate/popup/popup.js
+++ b/simple-translate/popup/popup.js
@@ -2,14 +2,15 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-let S = new settingsObj();
+const S = new settingsObj();
+const T = new Translate();
+
 //設定を読み出し
 S.init().then(function (value) {
     defaultTargetLang = value.targetLang;
-    targetLang = value.targetLang;
     secondTargetLang = value.secondTargetLang;
     ifChangeSecondLang = value.ifChangeSecondLang;
-    langList.value = targetLang; //リスト初期値をセット
+    langList.value = value.targetLang; //リスト初期値をセット
     langList.addEventListener("change", changeLang);
 
     document.body.style.fontSize = value.fontSize;
@@ -19,11 +20,9 @@ let target = document.getElementById("target");
 let langList = document.getElementById("langList");
 let textarea = document.getElementById("textarea");
 
-//langList= browser.i18n.getMessage("langList");
 const initialText = browser.i18n.getMessage("initialTextArea");
 textarea.placeholder = initialText;
 
-let targetLang;
 let secondTargetLang;
 let defaultTargetLang;
 let ifChangeSecondLang;
@@ -57,12 +56,13 @@ function alphabeticallySort(a, b) {
 }
 
 //翻訳先言語変更時に更新
-function changeLang() {
-    targetLang = langList.value;
-    if (sourceWord !== "") {
-        translate();
-    }
+async function changeLang() {
     if (typeof (url) != "undefined") showLink();
+
+    if (sourceWord !== "") {
+        const resultData = await T.translate(sourceWord, undefined, langList.value);
+        showResult(resultData.resultText, resultData.candidateText);
+    }
 }
 
 //アクティブなタブを取得して渡す
@@ -91,15 +91,15 @@ function getSelectionWord(tabs) {
 
 //ページ翻訳へのリンクを表示
 function showLink() {
-    document.getElementById("link").innerHTML = "<a href=https://translate.google.com/translate?hl=" + targetLang + "&sl=auto&u=" + encodeURIComponent(url) + ">" + browser.i18n.getMessage('showLink') + "</a>";
+    document.getElementById("link").innerHTML = "<a href=https://translate.google.com/translate?hl=" + langList.value + "&sl=auto&u=" + encodeURIComponent(url) + ">" + browser.i18n.getMessage('showLink') + "</a>";
 }
 
 //翻訳元テキストを表示
 function refleshSource() {
     if (sourceWord !== "") {
         textarea.innerHTML = sourceWord;
-        translate();
         resize();
+        inputText();
     }
 }
 
@@ -130,89 +130,49 @@ function textAreaClick() {
 }
 
 //文字入力時の処理
-function inputText() {
+async function inputText() {
     sourceWord = textarea.value;
-    translate();
+
+    const resultData = await T.translate(sourceWord, 'auto', langList.value);
+    changeSecondLang(defaultTargetLang, resultData.sourceLanguage, resultData.percentage);
+    showResult(resultData.resultText, resultData.candidateText);
 }
 
-//改行で分割してgetRequestに渡す
-function translate() {
-    let promises = [];
-    sourceLine = sourceWord.split("\n");
-    for (i = 0; i < sourceLine.length; i++) {
-        promises.push(getRequest(sourceLine[i]));
-    }
-    Promise.all(promises)
-        .then(function (results) {
-            showResult(results); //翻訳結果が帰ってきたらshowResult
-        });
-}
-
-//翻訳リクエストを送信，取得して返す
-function getRequest(word) {
-    return new Promise(function (resolve, reject) {
-        let xhr = new XMLHttpRequest();
-        xhr.responseType = 'json';
-        //let url = "https://translate.googleapis.com/translate_a/single?client=gtx&sl=auto&tl=" + targetLang + "&dt=t&q=" + encodeURIComponent(word);
-        let url = "https://translate.googleapis.com/translate_a/single?client=gtx&sl=auto&tl=" + targetLang + "&dt=t&dt=bd&q=" + encodeURIComponent(word);
-
-        xhr.open("GET", url);
-        xhr.send();
-        xhr.onload = function () {
-            resolve(xhr);
-        };
-    })
-}
-
-//翻訳結果を表示
-function showResult(results) {
+function showResult(resultText, candidateText) {
     const resultArea = target.getElementsByClassName("result")[0];
     const candidateArea = target.getElementsByClassName("candidate")[0];
-    resultArea.innerText = "";
-    candidateArea.innerText = "";
 
-    let resultText = "";
-    let candidateText = "";
-    let wordsCount = 0;
-    let lineCount = 0;
-
-    //第二言語に変更
-    if (ifChangeSecondLang) {
-        let lang = results[0].response[2];
-        let percentage = results[0].response[6];
-        if (targetLang == defaultTargetLang && lang == defaultTargetLang && percentage > 0 && !changeLangFlag) changeSecondLang();
-        else if ((lang != defaultTargetLang || percentage == 0) && changeLangFlag) unchangeSecondLang();
-    }
-    for (let j = 0; j < results.length; j++) {
-        lineCount++;
-        for (let i = 0; i < results[j].response[0].length; i++) {
-            resultText += results[j].response[0][i][0];
-        }
-        resultText += "\n";
-
-        if (results[j].response[1]) {
-            wordsCount++;
-            for (let i = 0; i < results[j].response[1].length; i++) {
-                const partsOfSpeech = results[j].response[1][i][0];
-                const candidates = results[j].response[1][i][1];
-                candidateText += `\n${partsOfSpeech}${partsOfSpeech!="" ? ": " : ""}${candidates.join(", ")}`;
-            }
-        }
-    }
     resultArea.innerText = resultText;
-    if (S.get().ifShowCandidate && wordsCount == 1 && lineCount == 1) candidateArea.innerText = candidateText;
+    if (S.get().ifShowCandidate) candidateArea.innerText = candidateText;
 }
 
 let changeLangFlag = false;
 
-function changeSecondLang() {
-    changeLangFlag = true;
-    langList.value = secondTargetLang;
-    changeLang();
-}
+function changeSecondLang(defaultTargetLang, sourceLang, percentage) {
+    //検出された翻訳元言語がターゲット言語と一致
+    const equalsSourceAndTarget = sourceLang == langList.value && percentage > 0;
 
-function unchangeSecondLang() {
-    changeLangFlag = false;
-    langList.value = defaultTargetLang;
-    changeLang();
+    //検出された翻訳元言語がデフォルト言語と一致
+    const equalsSourceAndDefault = sourceLang == defaultTargetLang && percentage > 0;
+
+    if (!changeLangFlag) {
+        //通常時
+        if (equalsSourceAndTarget && equalsSourceAndDefault) {
+            //ソースとターゲットとデフォルトが一致する場合
+            //ターゲットを第2言語に変更
+            changeLangFlag = true;
+            langList.value = secondTargetLang;
+            changeLang();
+        }
+    } else {
+        //第2言語に切替した後
+        if (!equalsSourceAndDefault) {
+            //ソースとデフォルトが異なる場合
+            //ターゲットをデフォルトに戻す
+            changeLangFlag = false;
+            langList.value = defaultTargetLang;
+            changeLang();
+
+        }
+    }
 }
diff --git a/simple-translate/simple-translate.css b/simple-translate/simple-translate.css
index d1f1603..e1ab841 100644
--- a/simple-translate/simple-translate.css
+++ b/simple-translate/simple-translate.css
@@ -65,6 +65,11 @@
 
 #simple-translate-panel .candidate {
     color: var(--simple-translate-sub-text);
+    margin-top:1em;
+}
+
+#simple-translate-panel .candidate:empty {
+    margin-top:0;
 }
 
 @keyframes simple-translate-showButton {
diff --git a/simple-translate/simple-translate.js b/simple-translate/simple-translate.js
index 5f12aa5..f9462c3 100644
--- a/simple-translate/simple-translate.js
+++ b/simple-translate/simple-translate.js
@@ -8,57 +8,54 @@ var panel = document.getElementById("simple-translate-panel");
 var selectionWord;
 var clickPosition;
 
-let S = new settingsObj();
+const S = new settingsObj();
+const T = new Translate();
 S.init();
 window.addEventListener("mouseup", Select, false);
 //テキスト選択時の処理 ダブルクリックした時2回処理が走るのを何とかしたい
-function Select(e) {
+async function Select(e) {
     hidePanel(e);
     if (e.target.tagName == "INPUT" && e.target.type == "password") return;
 
-    setTimeout(function () { //誤動作防止の為ディレイを設ける
-        if (e.target.tagName == "INPUT" || e.target.tagName == "TEXTAREA") {
-            selectionWord = e.target.value.substring(e.target.selectionStart, e.target.selectionEnd);
-        } else {
-            selectionWord = String(window.getSelection());
-        }
+    setTimeout(async () => { //誤動作防止の為ディレイを設ける
+        //選択文の取得 テキストフィールド内を選択した場合にも対応
+        const isTextField = (e.target.tagName == "INPUT") || (e.target.tagName == "TEXTAREA");
+        if (isTextField) selectionWord = e.target.value.substring(e.target.selectionStart, e.target.selectionEnd);
+        else selectionWord = String(window.getSelection());
 
-        if ((selectionWord.length !== 0) && (e.button == 0) && (e.target.id !== "simple-translate-panel") && (e.target.parentElement.id !== "simple-translate-panel")) { //選択範囲が存在かつ左クリックかつパネル以外のとき
-            clickPosition = e;
+        //選択文が存在し，パネル外を左クリックした場合は翻訳する
+        const existsSelectionWord = (selectionWord.length !== 0);
+        const isLeftClick = (e.button == 0);
+        const isPanelOutside = (e.target.id !== 'simple-translate-panel') && (e.target.parentElement.id !== 'simple-translate-panel');
+        const shouldTranslate = existsSelectionWord && isLeftClick && isPanelOutside;
+        if (!shouldTranslate) return;
 
-            checkLang().then(function (results) {
-                if (results) {
-                    switch (S.get().whenSelectText) {
-                        case 'showButton':
-                            popupButton(e);
-                            break;
-                        case 'showPanel':
-                            translate();
-                            showPanel(e);
-                            break;
-                        case 'dontShowButton':
-                            break;
-                    }
-                }
-            });
+        //選択した言語が翻訳先言語と異なれば翻訳する
+        const needTranslate = await checkLang(selectionWord, 'auto', S.get().targetLang);
+        if (!needTranslate) return;
+
+        clickPosition = e;
+        switch (S.get().whenSelectText) {
+            case 'showButton':
+                popupButton(e);
+                break;
+            case 'showPanel':
+                translate(selectionWord, 'auto', S.get().targetLang);
+                showPanel(e);
+                break;
+            case 'dontShowButton':
+                break;
         }
     }, 200);
 }
 
 //選択テキストの言語をチェックして返す
-function checkLang() {
-    return new Promise(function (resolve, reject) {
-        if (S.get().ifCheckLang) { //設定がオンなら
-            getRequest(selectionWord.substr(0, 100)) //先頭100文字を抽出して言語を取得
-                .then(function (results) {
-                    let lang = results.response[2];
-                    let percentage = results.response[6];
-                    resolve(lang != S.get().targetLang && percentage > 0); //真偽値を返す
-                });
-        } else { //設定がオフならtrueを返す
-            resolve(true);
-        }
-    })
+async function checkLang(sourceWord, sourceLang, targetLang) {
+    if (!S.get().ifCheckLang) return true; //設定がオフならtrue
+
+    const resultData = await T.translate(sourceWord, sourceLang, targetLang);
+    const needTranslate = (S.get().targetLang != resultData.sourceLanguage) && (resultData.percentage > 0);
+    return needTranslate; //ターゲットとソースの言語が不一致ならtrue
 }
 
 //ボタンを表示
@@ -89,71 +86,28 @@ function popupButton(e) {
     button.style.display = 'block';
 }
 button.addEventListener("click", function (e) {
-    translate();
+    translate(selectionWord, 'auto', S.get().targetLang);
     showPanel(e);
 }, false);
 
-//改行で分割してgetRequestに渡す
-function translate() {
-    promises = [];
-    sourceLine = selectionWord.split("\n");
-    for (i = 0; i < sourceLine.length; i++) {
-        promises.push(getRequest(sourceLine[i]));
-    }
-    Promise.all(promises)
-        .then(function (results) {
-            showResult(results); //翻訳結果が帰ってきたらshowResult
-        });
-}
-
-//翻訳リクエストを送信，取得して返す
-function getRequest(word) {
-    return new Promise(function (resolve, reject) {
-        let xhr = new XMLHttpRequest();
-        xhr.responseType = 'json';
-        let url = "https://translate.googleapis.com/translate_a/single?client=gtx&sl=auto&tl=" + S.get().targetLang + "&dt=t&dt=bd&q=" + encodeURIComponent(word);
-        xhr.open("GET", url);
-        xhr.send();
-        xhr.onload = function () {
-            resolve(xhr);
-        };
-    })
-}
-
-//翻訳結果を表示
-function showResult(results) {
-    panel.innerText = "";
-    let resultText = "";
-    let candidateText = "";
-    let wordsCount = 0;
-    let lineCount = 0;
-
-    for (let j = 0; j < results.length; j++) {
-        lineCount++;
-        for (let i = 0; i < results[j].response[0].length; i++) {
-            resultText += results[j].response[0][i][0];
-        }
-        resultText += "\n";
-
-        if (results[j].response[1]) {
-            wordsCount++;
-            for (let i = 0; i < results[j].response[1].length; i++) {
-                const partsOfSpeech = results[j].response[1][i][0];
-                const candidates = results[j].response[1][i][1];
-                candidateText += `\n${partsOfSpeech}${partsOfSpeech!="" ? ": " : ""}${candidates.join(", ")}`;
-            }
-        }
-    }
-    panel.innerHTML = "<p class=result></p><p class=candidate>"
-    panel.getElementsByClassName("result")[0].innerText = resultText;
-    if (S.get().ifShowCandidate && wordsCount == 1 && lineCount == 1) panel.getElementsByClassName("candidate")[0].innerText = candidateText;
+async function translate(sourceWord, sourceLang, targetLang) {
+    const resultData = await T.translate(sourceWord, sourceLang, targetLang);
+    showResult(resultData.resultText, resultData.candidateText);
     panelPosition(clickPosition);
+}
 
+function showResult(resultText, candidateText) {
+    panel.innerHTML = '<p class=result></p><p class=candidate>';
+    const resultArea = panel.getElementsByClassName("result")[0];
+    const candidateArea = panel.getElementsByClassName("candidate")[0];
+
+    resultArea.innerText = resultText;
+    if (S.get().ifShowCandidate) candidateArea.innerText = candidateText;
 }
 
 //パネル表示
 function showPanel(e) {
-    clickPosition = e;
+    clickPosition=e;
     panel.style.display = 'block';
     panelPosition(e);
 }
@@ -219,6 +173,6 @@ function sendToPopup() {
 //コンテキストメニュークリックでパネルを表示
 function showPanelFromMenu() {
     button.style.display = "none";
-    translate();
+    translate(selectionWord, 'auto', S.get().targetLang);
     showPanel(clickPosition);
 }
diff --git a/simple-translate/translate.js b/simple-translate/translate.js
new file mode 100644
index 0000000..4eb734d
--- /dev/null
+++ b/simple-translate/translate.js
@@ -0,0 +1,80 @@
+class Translate {
+    constructor() {
+    }
+
+    set sourceWord(word) {
+        this.sourceWord = word;
+    }
+
+    translate(sourceWord, sourceLang = 'auto', targetLang) {
+        //改行で分割
+        const sourceLines = sourceWord.split("\n");
+
+        let promises = [];
+        for (let sourceLine of sourceLines) {
+            promises.push(this.sendRequest(sourceLine, sourceLang, targetLang));
+        }
+
+        return new Promise(resolve => {
+            Promise.all(promises)
+                .then((results) => {
+                    resolve(this.formatResult(results));
+                });
+        });
+    }
+
+
+    sendRequest(word, sourceLang, targetLang) {
+        const url = `https://translate.googleapis.com/translate_a/single?client=gtx&sl=${sourceLang}&tl=${targetLang}&dt=t&dt=bd&q=${encodeURIComponent(word)}`;
+        const xhr = new XMLHttpRequest();
+        xhr.responseType = 'json';
+        xhr.open("GET", url);
+        xhr.send();
+
+        return new Promise((resolve, reject) => {
+            xhr.onload = () => {
+                resolve(xhr);
+            };
+        })
+    }
+
+    formatResult(results) {
+        const resultData = {
+            resultText: '',
+            candidateText: '',
+            sourceLanguage: '',
+            percentage: 0
+        }
+
+        //翻訳元言語を取得
+        resultData.sourceLanguage = results[0].response[2];
+        resultData.percentage = results[0].response[6];
+
+        let candidateText = '';
+        let wordCount = 0;
+        let lineCount = 0;
+
+        for (const result of results) {
+            lineCount++;
+
+            //翻訳文を取得
+            for (const response of result.response[0]) {
+                resultData.resultText += response[0];
+            }
+
+            //訳候補を取得
+            if (result.response[1]) {
+                wordCount++;
+                for (let i = 0; i < result.response[1].length; i++) {
+                    const partsOfSpeech = result.response[1][i][0];
+                    const candidates = result.response[1][i][1];
+                    candidateText += `${partsOfSpeech}${partsOfSpeech != '' ? ': ' : ''}${candidates.join(', ')}\n`;
+                }
+            }
+        }
+        //訳候補が一つの単語のみに対して存在するとき返す
+        if (wordCount == 1 && lineCount == 1) resultData.candidateText = candidateText;
+
+        return resultData;
+    }
+}
\ No newline at end of file