diff --git a/browser/components/CodeEditor.js b/browser/components/CodeEditor.js
index de542f49..a4d2278e 100644
--- a/browser/components/CodeEditor.js
+++ b/browser/components/CodeEditor.js
@@ -506,7 +506,7 @@ export default class CodeEditor extends React.Component {
         ref='root'
         tabIndex='-1'
         style={{
-          fontFamily: fontFamily.join(', '),
+          fontFamily,
           fontSize: fontSize,
           width: width
         }}
diff --git a/browser/lib/normalizeEditorFontFamily.js b/browser/lib/normalizeEditorFontFamily.js
index 290e452a..a2a2ec31 100644
--- a/browser/lib/normalizeEditorFontFamily.js
+++ b/browser/lib/normalizeEditorFontFamily.js
@@ -4,6 +4,6 @@ import isString from 'lodash/isString'
 export default function normalizeEditorFontFamily (fontFamily) {
   const defaultEditorFontFamily = consts.DEFAULT_EDITOR_FONT_FAMILY
   return isString(fontFamily) && fontFamily.length > 0
-    ? [fontFamily].concat(defaultEditorFontFamily)
-    : defaultEditorFontFamily
+    ? [fontFamily].concat(defaultEditorFontFamily).join(', ')
+    : defaultEditorFontFamily.join(', ')
 }
diff --git a/tests/lib/normalize-editor-font-family-test.js b/tests/lib/normalize-editor-font-family-test.js
new file mode 100644
index 00000000..aacd03ac
--- /dev/null
+++ b/tests/lib/normalize-editor-font-family-test.js
@@ -0,0 +1,16 @@
+/**
+ * @fileoverview Unit test for browser/lib/normalizeEditorFontFamily
+ */
+import test from 'ava'
+import normalizeEditorFontFamily from '../../browser/lib/normalizeEditorFontFamily'
+import consts from '../../browser/lib/consts'
+const defaultEditorFontFamily = consts.DEFAULT_EDITOR_FONT_FAMILY
+
+test('normalizeEditorFontFamily() should return default font family (string[])', t => {
+  t.is(normalizeEditorFontFamily(), defaultEditorFontFamily.join(', '))
+})
+
+test('normalizeEditorFontFamily(["hoge", "huga"]) should return default font family connected with arg.', t => {
+  const arg = 'font1, font2'
+  t.is(normalizeEditorFontFamily(arg), `${arg}, ${defaultEditorFontFamily.join(', ')}`)
+})