在採行「形式當事人主義」與「既判力相對性原則」的基礎上，為儘可能統一解決多數利害關係人間之紛爭，我國民事訴訟法設有一系列之「第三人訴訟參與」規範，而或允許第三人任意介入他人間之訴訟，或承認當事人、法院得將第三人引進本訴訟。其中，關於第三人事前主要參與之類型，相對於第三人得對原、被告提起主參加訴訟、原告得追加第三人為被告，民事訴訟法並未明文賦予被告單獨對第三人提起訴訟之權限，而呈現規範上之不對稱性，並進一步引發是否及如何承認「獨立第三人反訴」之疑問。本文乃一面參考德國、瑞士及法國法上對於類似問題之處理方式，歸納強制第三人訴訟參加制度所應考慮之因素，一面探討我國法上從事法之續造的正當性與必要性，提示「獨立第三人反訴」之審判模式。

In order to ensure the consistency of legal system as much as possible, it is crucial to apply the legal institutes of ＂involvement of third parties in the legal dispute＂ actively. This is due to the fact that under Taiwanese Code of Civil Procedure only claimant and defendant fall within the concept of ＂party＂. And except for situations prescribed in Art. 401 of the Code, any other stakeholder will be as a ＂third party＂ and not bounded by the judgement redndered in the case in which he or she was not involved. There is a series of provisions in the Code in relation to the involvement of third parties. Among thoese provisions, the legal institute of involving third party as ＂party＂ in a pending litigation is to be given special notice. One could namly seen an asymmetry under the Code: While third party could intervene voluntarily in an action by filing suits against the claimant and defendant, and claimant could force a third party to take part in the dispute by expanding his claim. However, the defendant is not explicitly allowed to cross-sue a third party. This leads to the question of whether the ＂isolated third party counterclaim＂ is admissible and, if so, which procedural rules should be followed. Aiming at resolving the mentioned problems properly, this article consults firstly the German, Swiss and French law; this comparative approach is justified on the grounds that, on the one hand, the Taiwanese civil procedural law has largely adopted the German law and, on the other hand, the Swiss law, which also belongs to the ＂German legal family＂, has fallowed to certain extent the French law. Based on results of the comparative study, this article will then reflecs on Taiwanese law and propose going beyond the scope of the current statute in terms of recognizing the ＂isolated third party counterclaim＂.