diff --git a/timer.js b/timer.js
index a3f7ef8..7089f36 100644
--- a/timer.js
+++ b/timer.js
@@ -14,7 +14,7 @@
         } else {
             infobox.innerHTML = count + "秒前";
             tmID = setTimeout(countDown, 1000);
-            document.getElementById('div').style.backgroundColor = 'red';
+            document.getElementById('box').style.backgroundColor = 'red';
         }
     }
     function startCountDown() {