This paper deals with the permission of Korean Family Court for an adoption. The amendment of Korean Family Law in 2012 introduced an adoption system which requires the permission of Family Court when an adoptee is minor. Until then, Korean adoption system required just both consents of an adopter and an adoptee. When an adoptee was under 15, the consents of his/her parents or guardian should be granted instead of the consent of the adoptee. Korean Family Court took no part in adoptions at that time. The amendment in 2012 attempted to expand the function of Korean Family Court in the family law field. It shall be estimated much positively. When an adoption is made inside Korea, this amendment is very understandable. If it is made by Korean people outside Korea, how does the amendment work to the adoption, especially Korean people residing in Japan? This is the main purpose of this paper. When a Korean couple makes an adoption in Japan, Korean Law shall be applied to this case according to Article 31 of Japanese Private International Law(Ho no Tekiyou ni Kansuru Tsusokuho). Thus, they are required requisites stipulated in Korean Family Law. The above permission of Korean Family Court is also necessary for the adoption. Of course, there is no Korean Family Court inside Japan. But Japanese Family Law has the similar system in which Family Court’s permission is required in an adoption when an adoptee is minor. In this situation, the Korean Supreme Court which directs the nation registry, has decided it relating to the nation registry that the permission of Japanese Family Court can’t take place the permission of Korean Family Court in adoptions. On the contrary to this decision, this paper insists on the substitution of Japanese Family Court in such cases. General speaking, the theory of Private International Law tries to admit substitution to systems of applicable law in the forum’s systems. It shall be admitted when both systems are almost same in functions, purposes, proceedings and so on. This paper analyses the high similarity of both Family Court’s permissions. Therefore, Japanese Family Court’s permission shall be substitute to Korean Family Court’s permission in an adoption when an adoptee is minor.