diff --git a/www/index.php b/www/index.php
index e5fa328..52ab6b8 100644
--- a/www/index.php
+++ b/www/index.php
@@ -29,6 +29,16 @@
       exit;
     }
 
+    if (strlen($newadd) > 500) {
+      $title = '076エラー - 不正なURL';
+      $h1 = '【エラー】URLは長すぎ';
+      $bg = 'daityan';
+      $bgpos = 'top right 100px';
+      $err = 'URLは500文字以内です。';
+      include_once('../views/404.php');
+      exit;
+    }
+
     $data = file_get_contents('links.json');
 
     $arr = json_decode($data, true);