[2] The meaning of "serious negligence" in the motive mistake

[3] Requirements and validity of partial revocation of a juristic act

[2] When the motive mistake is caused by the gross negligence of the observer, the term "serious negligence" here refers to the lack of attention that is ordinarily required in light of the name of the observer, the type and purpose of the act, etc.

[3] Even if there is a ground for revocation only for a part of a single juristic act, if the juristic act is divisible or part of the subject matter can be specified, the remaining part may be revoked if the party's assumptive intent to maintain it is acknowledged. The partial revocation becomes effective as to the part of the juristic act.

1. On the first ground for appeal

A. In order to cancel a juristic act on the ground that the motive mistake constitutes an error in an important part of the contents of the juristic act, it is sufficient to indicate the motive to the other party as the content of the pertinent declaration of intent, and it is necessary to conclude that the parties have agreed to separately consider the motive as the content of the juristic act (see, e.g., Supreme Court Decisions 88Meu31507, Dec. 26, 1989; 95Da5516, Nov. 21, 1995). However, the mistake in the contents of the juristic act must be related to an important part so long as it would have been deemed that the general public would not express such intent (see, e.g., Supreme Court Decisions 87Meu1271, Jan. 17, 1989; 93Da55487, Mar. 26, 1996).

B. The facts acknowledged by the court below are as follows.

(1) On March 195, the Plaintiff: (a) entrusted the implementation of the project for compensation for land to be incorporated into the Incheon Airport Highway Construction Project implemented by the Ministry of Construction and Transportation and the Korea Highway Corporation; (b) as the instant land was incorporated into the relevant road site; and (c) requested the Defendants, the owner of the instant land, to negotiate with the Defendants in order to acquire the land in accordance with the procedures set forth in the Public

(2) The Plaintiff, prior to the above consultation on December 30, 1994, requested an appraisal of the price of the land to the non-party regular appraisal corporation and the central appraisal corporation for the purpose of determining the price as prescribed by the Special Act on the Law on the Law on the Law of the Law of the Law of the Law of the Law of the Law of the Law of the Law of the Law of the Law of the Law of the Law of the Law of the Law of the Law of the Republic of Korea. On January 26, 1995, the above central appraisal corporation received 76,00 won, and the above central appraisal corporation received 75,000 won, which is an arithmetic mean of the two appraisal values

(3) As a result, from March 7, 1995 to April 6, 1995, the purchase price was determined based on 75,000 won per square meter and the amount was established between the Plaintiff and the Defendants. Accordingly, the Plaintiff entered into a contract to purchase the instant land from the Defendants, and thereafter, paid each corresponding amount to the Defendants around that time.

(4) According to Article 6(4) of the Enforcement Rule of the Public Special Act, land subject to restrictions in the public law is assessed as limited condition except for the case where the restriction in the public law directly aims at the implementation of the public project in question, and is assessed as proper reduction in consideration of the degree of restriction, and the use of the land in this case is designated as a natural green belt development restriction zone. However, the above two appraisal corporations discovered that the land in this case was mistakenly assessed as a green belt development restriction zone as a production green belt due to error in the recognition in the initial evaluation of the land in this case on April 28, 1995, after the purchase by consultation, and that the land in this case was mistakenly assessed as a production green belt. The appraisal corporation in this case was 41,00 won for the land in this case, and the central appraisal corporation in this area notified the Plaintiff of a correction statement prepared again as 40,000 won in this time, and the Plaintiff requested the Plaintiff to refund the purchase price in this case to 50,500 won per square meter.

(5) On February 21, 1995, when the Plaintiff requested consultation with the Defendants, the Plaintiff notified and presented in writing the amount calculated by calculating the arithmetic mean of the values appraised by two appraisal agencies according to the method prescribed by the Special Act on Public Law, and accordingly, notified and presented in advance the amount calculated by calculating 75,000 won per square meter. After doing so, at the time of entering into a contract with the Defendants, it explained such details at the time of entering into a contract with the Defendants, and at the time of entering into a contract with the Defendants, the indication of the “sale contract” column entered the unit price and area in the “sale contract” column, as well as at the time of determining the price in accordance with Article 1(1) of the Sales Contract, the “price was determined by mutual agreement between the Defendants pursuant to Article 4 of the Special Act on Public Law and Article 2(1) of the Enforcement Decree of the same Act. The Nonparty, who received an excessive payment with the Defendants, returned the excessive amount to the Plaintiff according to the Plaintiff’s request for return.

C. Based on the above facts, the lower court determined as follows.

(1) The Plaintiff entered into a contract by presenting the purchase price to the price as a result of an erroneous mistake with the knowledge that the arithmetic mean of the market price per 75,000 square meter price was 75,000, based on the appraised value by two appraisal agencies. Such an error constitutes a motive mistake as a mistake in the market price of an object. The Plaintiff notified the Defendants in writing of the method of determining the purchase price at the time of their request for purchase. The Defendants, recognizing such circumstance, and indicating the criteria for and calculation details of the purchase price and the method thereof in the sales contract, thereby making the motive of expressing their intent.

(2) The sales price is corresponding to the nature of the subject matter, which is the major part of the sales contract, and the price increases and decreases under the market economy. As such, even if there are some differences due to mistake in determining the amount of the purchase price, ordinary damages do not constitute an error in the important part. However, in this case, where the amount of the purchase price is assessed as either 85% or more based on the legitimate appraised value, and the degree of difference in the price is significant, and the Plaintiff, as a local government, purchases land necessary for the business through the procedure of expropriation, etc. in a case where a consultation is not effected or no agreement is reached. In light of such circumstances, it is evident that the Plaintiff would not enter into a sales contract on the basis of an excessive amount assessed as such if there was no error in the above motive. Accordingly, it is reasonable to deem that the motive for the Plaintiff’s determination of the amount of the purchase price constitutes an important part of the contents of the purchase agreement in this case.

(3) Although the market price of the Plaintiff is a competent administrative agency, it is difficult for the Plaintiff to compare and review the land to be incorporated into a road by the same project other than the land in this case, and its use, status, etc. is not easy. Moreover, since the market price appraisal of the land is assessed not only in the specialized area of the assessment agency, but also in consideration of various factors such as the officially announced land price, land price rate, regional factors, and individual factors, it is very difficult for the Plaintiff to review the appropriateness of the appraised value and find errors. Furthermore, as in this case, if two appraisal agencies concurrently and simultaneously cause errors, it is difficult to say that the Plaintiff would have any actual trust in the Plaintiff. In light of these circumstances, it is difficult to deem that the Plaintiff was negligent by gross negligence on the ground that the Plaintiff concluded a contract based on the belief of the contents of the appraisal report by the two appraisal agencies, without thoroughly examining the use of the land in this case and the contents of the appraisal report.

D. The judgment of the court below is just in accordance with the above legal principles, and there is no error of law such as misapprehension of legal principles as the theory of lawsuit. The argument is without merit.

2. On the second ground for appeal

Even if a part of a juristic act is subject to grounds for revocation, if the juristic act is separate or certain, it may be possible to revoke that part of the juristic act if the party’s assumptive intent is recognized even in the remaining part, and such revocation shall take effect as to the part of the juristic act (see Supreme Court Decisions 90Meu7460, Jul. 10, 1990; 91Da36062, Feb. 14, 1992).

For the reasons indicated in its holding, the court below's decision that the contract of this case between the plaintiff and the defendants was retroactively null and void only within the applicable scope due to the plaintiff's partial revocation of the plaintiff's expression of intent on the ground of the above mistake is just in accordance with the above legal principles, and there is no error of law such as misunderstanding of legal principles or incomplete hearing, etc.

3. Therefore, all appeals are dismissed, and the costs of appeal are assessed against the losing party. It is so decided as per Disposition by the assent of all participating Justices on the bench.

Justices Lee Im-soo (Presiding Justice)