1. The plaintiff (Counterclaim defendant)'s appeal against the principal lawsuit is dismissed.

2. The part concerning the counterclaim of the first instance judgment is as follows.

A principal lawsuit and a counterclaim shall be deemed simultaneously.

1. On May 6, 2013, the Plaintiff, who runs wholesale and retail business of the Plaintiff’s main construction machinery wholesale and retail business, on the grounds of the Plaintiff’s claim for the main construction machinery, only one unit of the CNC mining center, the Model PMA400LB (hereinafter “instant machinery”).

) The fact that the Plaintiff sold the instant machinery to KRW 148,50,000 (including value-added tax of KRW 13,500,000) (hereinafter “instant sales contract”) and around June 27, 2013 is not a dispute between the parties, and the Plaintiff received KRW 135,00,000 from the Defendant for the purchase price.

Therefore, the Defendant is obligated to pay the remainder of KRW 13,500,000 (=148,500,000 - 135,000,000) and damages for delay, barring special circumstances, to the Plaintiff.

2. Judgment on the defendant's defense and the ground for counterclaim against the principal lawsuit

A. The summary of the Defendant’s assertion 1) there is a defect in the machinery of this case that the Defendant did not have the required performance, and as such, the Defendant asserted that it did not have the obligation to pay any balance of the purchase price, and at the same time, the Defendant purchased the machinery of this case by mistake as to the machinery performance of this case. 2) The Defendant asserted that the instant sales contract was revoked on the grounds of such mistake, and at the same time, the Defendant asserted that it did not have the obligation to pay any balance of the purchase price, and sought a refund of the purchase price that the Defendant paid to the Plaintiff as a counterclaim.

B. For the purpose of assessing that there is a defect in the subject matter of determination on the rescission of the instant sales contract due to the instant mechanical defect, even if the goods supplied to the buyer are not equipped with ordinary quality or performance, or the buyer is equipped with ordinary quality or performance.