After Enforcement Rules on the Operation of Joint Contracts was amended by Ministry of Strategy and Finance in Jan. 8, 1996, judicial opinions on how claims of construction costs shall belong to the partners of joint venture changed, but it was not clear. That is, if the parties express their intention to exclude the application of civil code provisions on the partnership-ownership, the claims of construction costs may belong to each partners separately. Subsequent judicial precedents did not come to a unified conclusion. In some cases it was concluded that the claims belonged to all the partners jointly, but in others it was not. In other cases of similar issues, while admitting that a joint venture is a civil partnership, obligations to return advance payment was settled separately by each partners. Contradictory precedents left the following questions: Is a joint venture a civil partnership? Is the legal nature of the civil code provisions on the partnership-ownership of partnerships compulsory or optional? In conclusion, can the claims for construction costs of joint ventures belong to each of the partners?<BR> Supreme Court en banc Decision 2009Da105406 decided May 17, 2012 made decisions that a joint venture is a civil partnership under civil code, and that the claims for construction costs of the joint ventures belong to each of its partners separately under special agreements of a contract for a construction work. But the Supreme Court Decision was not clear and still left the following problems; Which of the provision on partnership-ownership under civil code is interpreted as optional? Are these opinions generally applicable to a civil partnership? What does it mean that the attribution method on claims of a civil partnership can be laid down under special agreements of a contract for construction work?<BR> Experts in favor of the Supreme Court Decision say that it is based on the principle of freedom of contract. Opposite views, on the other hand, presuppose that the provisions of civil code, which define the method of belonging to the property of civil partnership, are compulsory. However, the specific solutions proposed by each opinion are various.<BR> The property of a civil partnership include everything with value as property. How this is attributed to partners is defined in § 271 (1) in part of Real Rights and § 704 in part of Claims. With regard to the relationship between the two articles, it is generally considered either that they duplicate one another or that § 704 is unnecessary. However, contrary to the opinion of the above theory, if § 271 (1) and § 704 can be assumed to have different meanings, § 271 could have the meaning of forcing only real right property to belong to partners, not all property of a civil partnership. So the attribution of claims of a civil partnership is determined by § 704. In short, the property of civil partnership as real rights is ruled by compulsory provisions on Partnership-ownership in Real Rights, the property of civil partnership as claims is ruled by a optional provision on Partnership-ownership in Claims.<BR> If such assumptions are allowed, the claims of a civil partnership, in principle, belong to the partners in accordance with § 704. However, if there are special agreements in the partnership contract that divide the claims of the civil partnership into partners, this implies the exclusion of § 704, so the attribution of the claims becomes as agreed by the partners. However, even if the special agreements exist in the agreement between the partnership and the third party, they do not define how the property of the partnership belongs. This is because matters related to the internal relationship of partnerships can be determined only by the terms of the partnership contract. These special agreements, in some cases, can only mean how third parties can implement their contracts.<BR> In conclusion, the meanings of Supreme Court en banc Decision in 2012 could be found as follows. First, as before, § 271 (1) is a compulsory provision. Second, § 704 is an optional provision. One of the cases where § 704 is applied is the construction costs of the joint venture. Third, the property of a civil partnership where § 704 is applied is different from that where § 271 (1) is applied. In addition, an opinion that makes clear that the legal nature of the joint venture is a civil partnership means the above conclusions are generally applicable to civil partnerships. However, care should be taken when reading the expression, “The claims for construction costs of the joint ventures belong to each of its partners separately under special agreements of a contract for construction work.” It means that partners own the claims for construction costs separately, not