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="首頁" />
      <page pageid="1278" ns="0" title="刪除-地球的孩子779-快樂七隻腳" />
      <page pageid="3055" ns="0" title="待刪除02" />
      <page pageid="3622" ns="0" title="待刪除" />
    </pages>
  </query>
</api>