Whether or not there exists a creditor's right to the debtor to be preserved by subrogation in a creditor subrogation lawsuit is an ex officio investigation of the court as a requirement for the lawsuit. Thus, even if the court does not have an obligation to detect ex officio the facts and evidence, which are basic data for the judgment, even if it is not a duty to detect ex officio the facts and evidence, if any circumstance to suspect the existence of the preserved claim is discovered by examining all the litigation data presented to the court, the court has a duty to ex officio verify

According to the reasoning of the judgment below, the court below rejected the creditor subrogation lawsuit of this case on the premise that the plaintiff owned the preserved claim of this case against the non-party 1, who is the debtor, on behalf of the non-party 1, for the purpose of preserving the loan claim of KRW 87.5 million against the non-party 1 (hereinafter "the preserved claim of this case"). Since the plaintiff transferred the preserved claim of this case to the non-party 2 around August 2005, the court below rejected the creditor subrogation lawsuit of this case on the premise that the plaintiff owned the preserved claim of this case against the non-party 1, the debtor

However, according to the evidence evidence No. 3 attached to the record, the purpose of which the officer participating in the Busan District Court again grants to the plaintiff the execution clause succeeded to the final judgment of the preservation claim of this case as of October 13, 2006 under the order of the judicial assistant officer, and the succeeding execution clause is granted only when the succession is obvious to the court or when the succession is verified by a certificate (Article 31, Article 32 of the Civil Execution Act, Article 2 (1) 4 of the Rules of the Judicial Assistant officer). Examining the circumstances known through the record, such as the presiding judge (Article 31, Article 32 of the Civil Execution Act, Article 2 (1) 4 of the Rules of the Judicial Assistant Official). The court below neglected ex officio the duty to confirm the existence of the preservation claim of this case through additional review and investigation, and thus, the plaintiff's subrogation lawsuit of this case was unlawful. The ground for appeal pointing this out has merit.

Therefore, the judgment of the court below is reversed, and the case is remanded to the court below for a new trial and determination. It is so decided as per Disposition by the assent of all participating Justices on the bench.

Justices Cha Han-sung (Presiding Justice)