The defendant may file a counterclaim with the court where the principal action is pending up until the time that oral arguments reach a conclusion, but only if the subject matter of the counterclaim is a claim with a bearing on the claim that is the subject matter of the principal action or with a bearing on the means of defense; provided, however, that this does not apply in the following cases:
被告は、本訴の目的である請求又は防御の方法と関連する請求を目的とする場合に限り、口頭弁論の終結に至るまで、本訴の係属する裁判所に反訴を提起することができる。ただし、次に掲げる場合は、この限りでない。
if the claim that is the subject matter of the counterclaim is subject to the exclusive jurisdiction of another court (excluding one determined by an agreement between the parties pursuant to the provisions of Article 11);
反訴の目的である請求が他の裁判所の専属管轄（当事者が第十一条の規定により合意で定めたものを除く。）に属するとき。
if the filing of a counterclaim would substantially delay litigation proceedings.
反訴の提起により著しく訴訟手続を遅滞させることとなるとき。
If the principal action is pending before a court specified in any of the items of Article 6, paragraph (1), and the claim that is the subject matter of the counterclaim is subject to the exclusive jurisdiction of another court pursuant to the provisions of paragraph (1) of that Article, the provisions of item (i) of the preceding paragraph does not apply.
If the Japanese courts have no jurisdiction over a claim that is the subject matter of a counterclaim, the defendant may file a counterclaim pursuant to the provisions of paragraph (1) only if the subject matter of the counterclaim is a claim with a close bearing on the claim that is the subject matter of the principal action or with a close bearing on the means of defense; provided, however, that this does not apply if the Japanese courts have no jurisdiction over the claim that is the subject matter of the counterclaim pursuant to the provisions on exclusive jurisdiction.
日本の裁判所が反訴の目的である請求について管轄権を有しない場合には、被告は、本訴の目的である請求又は防御の方法と密接に関連する請求を目的とする場合に限り、第一項の規定による反訴を提起することができる。ただし、日本の裁判所が管轄権の専属に関する規定により反訴の目的である請求について管轄権を有しないときは、この限りでない。
Counterclaims are governed by the provisions on actions.
反訴については、訴えに関する規定による。