You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <pages>
      <page pageid="141" ns="0" title="JUNKWIKI" />
      <page pageid="149" ns="0" title="PC用電源OEM元" />
      <page pageid="343" ns="0" title="サーバー構築方法（Linux編）" />
      <page pageid="222" ns="0" title="デジイチ入門" />
      <page pageid="2" ns="0" title="所有PC環境" />
      <page pageid="224" ns="0" title="所有パーツ" />
      <page pageid="234" ns="0" title="画像募集" />
      <page pageid="181" ns="0" title="自宅サーバーを始めるあなたに" />
    </pages>
  </query>
</api>