The case is remanded to the Gwangju High Court.

According to the judgment of the court below, on January 20, 1961, the plaintiff's house offered full payment of the remaining amount to the plaintiff's house, but the plaintiff failed to provide the documents for cancellation of the registration of the establishment of the right to collateral security at the real estate at the same time, but the defendant paid only 100,00 won out of the remaining amount to the plaintiff, and the above date after the delivery of the documents for the establishment of the right to collateral security or the registration of the establishment of the right to collateral security at the same time, the plaintiff cancelled the registration of the right to collateral security on February 3, 1962 after the cancellation of the registration of the establishment of the right to collateral security on this real estate and prepared the documents for the registration of the right to collateral security (20,000 won) to the defendant to pay the remaining amount (20,000 won) within 10 days after the expiration of the sale contract at the same time, and it can be acknowledged that the plaintiff did not have any right to request the plaintiff to present the above notice at the above 20-day.

However, it is reasonable to interpret that if one of the parties has provided performance according to the principal of the obligation and the other party has continued to provide performance even if the other party has not performed the obligation, if it is not known that the other party has provided performance once in the past, it does not lose the right of defense of simultaneous performance as to payment (see Supreme Court Decision 66Da1174 delivered on September 20, 1966, 196, 66Da1174 delivered on September 20, 196). In this case, even if the original due date for performance expires, the above two obligations are in the relation of simultaneous performance without fixed time. In this case, even if one of the parties has provided performance and requested the other party to perform the obligation, if the other party has failed to perform the obligation despite having requested the other party to perform the obligation, the party is liable for the other party's right to rescission. Accordingly, in this case, even if the other party has provided the obligation at the initial date for the performance of the obligation, the plaintiff has not provided the obligation to the other party at the same time.

In addition, in a real estate sales contract where the obligation to pay for the purchase and sale of real estate and the obligation to pay for the registration of ownership transfer is in a simultaneous performance relationship, the performance of the registration procedure requires an act of the other party, so it is sufficient to provide an objection to the existence of an objection by completing the preparation of all documents necessary for the registration procedure to the extent that the real estate can be offered at any time, and by notifying the other party to receive it (see Supreme Court Decision 69Da1223, Apr. 14, 1960). It is reasonable to interpret that the ownership of the registration document does not necessarily require a real provision of the documents to the other party (see Supreme Court Decision 69Da1223, Apr. 14, 1960). Therefore, in this case, the court below did not examine the facts that the defendant prepared all the documents required for the registration of ownership transfer as alleged by the plaintiff and required the defendant to attend the registration office on the last day of the maximum period, and there is no error in the misapprehension of the court below's judgment or the reasons for cancellation of the contract or cancellation.

Therefore, it is so decided as per Disposition by the assent of all participating Justices.

[Judgment of the Supreme Court (Presiding Judge) Nabri-dong and Dobri-Jaking Hanwon