Wider Admin Menu is a standalone plugin built, maintained & operated by the friendly folks over at MachoThemes.
Wider Admin Menu is a lightweight plugin that lets you set the width of your admin menu from the default 160px up to 300px.
A separate stylesheet is also included if you wish to avoid Yet Another Plugin. See FAQ.
This plugin will leave no trace! If you delete the plugin, all settings will be removed from the database. Guaranteed. However, simply deactivating it will leave your settings in place, as expected.
このプラグインをダウンロードして、インストール型 WordPress のインストールに使用できます。