diff --git a/create_user.php b/create_user.php
index 2883b17..d28d0ff 100644
--- a/create_user.php
+++ b/create_user.php
@@ -12,6 +12,7 @@ $user = new User;
 $user -> name = $_GET['name'];
 $user -> pass = implode (
     array_map (fn () => $chars[rand (0, strlen ($chars) - 1)], range (1, 8)));
+$user -> inheritance_code = implode (array_map (fn () => rand (0, 9), range (1, 12)));
 
 echo [$user -> insert () -> id];
 
diff --git a/migrations/2023_07_13_122000_add_columns_to_users_table.sql b/migrations/2023_07_13_122000_add_columns_to_users_table.sql
new file mode 100644
index 0000000..6bb15bc
--- /dev/null
+++ b/migrations/2023_07_13_122000_add_columns_to_users_table.sql
@@ -0,0 +1,2 @@
+ALTER TABLE `users` ADD `inheritance_code` VARCHAR(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL COMMENT '引継ぎコード' AFTER `pass`, ADD `created_at` DATETIME NOT NULL AFTER `inheritance_code`, ADD `modified_at` DATETIME on update CURRENT_TIMESTAMP NOT NULL AFTER `created_at`, ADD `deleted_at` DATETIME NULL DEFAULT NULL AFTER `modified_at`;
+
diff --git a/modules/user.mod.php b/modules/user.mod.php
index a5be820..8fd1789 100644
--- a/modules/user.mod.php
+++ b/modules/user.mod.php
@@ -6,6 +6,7 @@ User
   var $id;
   var $name;
   var $pass;
+  var $inheritance_code;
 
   public static function
   find (
@@ -28,6 +29,7 @@ User
     $self -> id = $id;
     $self -> name = $row['name'];
     $self -> pass = $row['pass'];
+    $self -> inheritance_code = $row['inheritance_code'];
 
     return $self;
   }
@@ -38,8 +40,16 @@ User
   {
     $sql = "
         INSERT INTO
-          users  (name,              pass)
-          VALUES ('{$this -> name}', '{$this -> pass}')";
+          users (
+            name,
+            pass,
+            inheritance_code,
+            created_at)
+          VALUES
+            ('{$this -> name}',
+             '{$this -> pass}',
+             '{$this -> inheritance_code}',
+             NOW())";
     $GLOBALS['__db_connection'] -> query ($sql)
         or die ("db_insert error $sql");