Code of Civil Procedure Article 507-2

In matters of a third-party opposition action, the original court which entered the opposed judgment has exclusive jurisdiction.In matters of a third-party opposition action jointly filed against the judgments entered on the same matter by courts of different instances, or merely against the judgment entered by the superior court, the original court of second instance has exclusive jurisdiction. Where no judgment has ever been entered by the court of second instance, the original court of first instance has exclusive jurisdiction.
中文原文 民事訴訟法第507-2條
第三人撤銷之訴,專屬為判決之原法院管轄。
對於審級不同之法院就同一事件所為之判決合併提起第三人撤銷之訴,或僅對上級法院所為之判決提起第三人撤銷之訴者,專屬原第二審法院管轄。
其未經第二審法院判決者,專屬原第一審法院管轄。

English translation for reference only; the Chinese text prevails. Not legal advice.