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-continue>
    <allfileusages gafcontinue="China_Yunnan_nasi.png|457" />
  </query-continue>
  <query>
    <pages>
      <page pageid="4" ns="0" title="アダパについて" />
      <page pageid="366" ns="0" title="地平線の太陽：ヒエログリフ" />
      <page pageid="433" ns="0" title="全ての道は西安に通ず" />
      <page pageid="511" ns="0" title="リングと太陽の鳥" />
      <page pageid="524" ns="0" title="巴蜀の目：甲骨文字" />
      <page pageid="627" ns="0" title="蛙の炎帝神農：甲骨文字" />
    </pages>
  </query>
</api>