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="1" ns="0" title="Main Page" />
      <page pageid="3" ns="0" title="PC構成" />
      <page pageid="4" ns="0" title="PC用電源OEM元&amp;神小話" />
      <page pageid="186" ns="0" title="サーバ部を始めるあなたに" />
      <page pageid="193" ns="0" title="メインページ" />
      <page pageid="223" ns="0" title="一眼レフ入門" />
      <page pageid="224" ns="0" title="所有パーツ" />
      <page pageid="297" ns="0" title="ロゴ募集" />
      <page pageid="347" ns="0" title="サーバー構築方法Linux編" />
    </pages>
  </query>
</api>