diff --git a/popup__iframe.html b/popup__iframe.html
index 9351ee01..d461d20f 100644
--- a/popup__iframe.html
+++ b/popup__iframe.html
@@ -221,6 +221,10 @@
         </div>
       </div>
       <div style="display: none;" class="mouse__config mouse__config--speed text-center">
+        <div class="help-text--mouse-speed text-left">
+          <p>Press this key along with mouse movement/scrolling to accelerate/decelerate the speed of the action.</p>
+          <p>You can set the multiplier in <a href="#" title="link to the setting">link to setting</a>.</p>
+        </div>
         <div class="btn-group btn-group-lg" role="group">
           <button type="button" class="btn btn-default">-</button>
           <button type="button" class="btn btn-default">+</button>
diff --git a/sass/style.scss b/sass/style.scss
index 70fcc4b7..ed62bad2 100644
--- a/sass/style.scss
+++ b/sass/style.scss
@@ -177,3 +177,15 @@
     }
   }
 }
+
+.help-text {
+  &--mouse-speed {
+    margin-bottom: 2rem;
+    font-size: .9em;
+    color: #666;
+
+    p {
+      margin: 0;
+    }
+  }
+}