1. The plaintiff's claim is dismissed.

2. The costs of lawsuit shall be borne by the Plaintiff.

1. Determination as to the cause of claim

A. The gist of the Plaintiff’s assertion was that the Plaintiff purchased the CNCton Machines (hereinafter “instant machinery”) from the Defendant, but there was a significant defect in the machinery from the time of the purchase to the point of repair, and thus, the seller’s warranty liability (Article 580(1) of the Civil Act) was rescinded, or the Plaintiff purchased the instant machinery without knowing the important defect, and there was an error in the important part of the content of the legal act. Therefore, the sales contract was revoked pursuant to Article 109(1) of the Civil Act. As such, the Defendant paid to the Plaintiff KRW 37,570,000,000,000 won for the instant machinery, KRW 577,000,000 for contractual penalty, and damages for delay.

B. The proviso of Article 580(1) of the Civil Act provides that the warranty liability may not be revoked in the event that the Plaintiff was unaware of the defect due to negligence, and the proviso of Article 109(1) of the Civil Act provides that the error may not be revoked in the event of gross negligence. In light of the above provision, even if there were serious defects in the instant machinery, the parties are not interested in the dispute, and the overall purport of the entry of evidence No. 3 and arguments can be considered as follows: ① both the Plaintiff and the Defendant appear to be not an expert on the instant machinery; ② in light of the Plaintiff’s acquisition of the instant machinery for about 16 years and over 16 years in the manufacturing year, the Plaintiff could have easily known that the defect of the instant machinery had been done in an appropriate manner with due care, and thus, the Plaintiff could have easily found the defect of the instant machinery if the Plaintiff had done trial operation of the instant machinery by gross negligence.