1. The defendant's appeal is dismissed.

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

3. The judgment of the court of first instance is subject to Paragraph (1).

1. The reasoning of the judgment of the court of first instance is as follows, and the same reasoning of the judgment of the court of first instance is as follows, except for the part that was used for the 8th and 12th and 9th of the judgment of the court of first instance as follows. Thus, this is acceptable pursuant to the main sentence of Article 420 of the

2. Determination as to the defendant's defense 4)

A. The defendant has a duty of care to verify whether the plaintiffs can build a building on each of the lands of this case, but it did not verify it properly and it was grossly negligent for them to conclude a sales contract. Thus, the defendant has a defense to the effect that the sales contract of this case cannot be revoked.

B. When there is an error in the important part of the contents of a juristic act, the declaration of intention may be cancelled, but such error may not be cancelled if it was caused by gross negligence of the person who indicated, and the term "serious negligence" in this context refers to a lack of care normally required in light of the name, type, purpose, etc. of the person who indicated the

(See Supreme Court Decision 96Da26657 delivered on August 22, 1997, and Supreme Court Decision 2002Da70884 delivered on April 11, 2003, etc.).

In light of the above legal principles, the following facts and circumstances, which are recognized by comprehensively considering the evidence and the purport of the entire pleadings, were found to have been found to have been erroneous as to whether the plaintiffs can construct a building on each of the lands of this case, and it is difficult to view that the contract of this case was concluded with the purchaser of the land lacks the due diligence generally required, and there is no other evidence to acknowledge that the above mistake

Therefore, the defendant's above defense is not accepted.

① Around 2015, the Defendant requested I to introduce a person to purchase the instant land before the instant partition to I, etc., and I, at the beginning of 2017, get off the instant land from A, who is his/her wife, and pentate.