1. The plaintiff's appeal is dismissed.

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

The purport of the claim and appeal is the purport of the appeal.

1. Determination on the cause of the claim

A. The Plaintiff’s assertion and business concluded a sales contract with the Defendant on the one of the Jindo boiler (hereinafter “instant boiler”) (hereinafter “instant sales contract”), and the Defendant installed the said boiler at the Plaintiff’s place of business.

In light of the above boiler’s failure to perform its duty under the principle of good faith to notify and explain such circumstances to the Plaintiff, and thereby deceiving the Plaintiff, and the Plaintiff concluded the instant sales contract by causing mistake.

Therefore, the cancellation of the instant sales contract and the restitution of KRW 18,900,000 paid to the Defendant as the restitution, and the delayed payment is sought.

B. The facts of recognition 1) comprehensively taking account of Gap evidence Nos. 1 and 4 and the result of on-site inspection conducted by the court of first instance on January 20, 2016, the plaintiff entered into a contract with the defendant on December 3, 2013 to purchase the boiler in this case at KRW 18,50,000, and the defendant established it at the plaintiff's workplace, and the plaintiff paid KRW 18,90,000 to the defendant until February 7, 2014, the boiler in this case was suspended after about five minutes since its operation, and the fact that the plaintiff sent to the defendant on February 16, 2015 that the above content-certified mail reached the defendant around that time is acknowledged as follows.

① There is no error in the Defendant’s installation of the boiler of the instant case, and the suspension of the operation of the boiler of the instant case on a regular basis is deemed due to the lack of the vibration of the boiler.

② At least the stoves, such as the boiler, are in the same state.