The purpose of this study is to deal with the succession problem of North Korea-China Border Treaty andMaritime Boundary Agreement. Now, the existence of North Korea-China Border Treaty was identifiedinofficially. The national border treaty between the Democratic People’s Republic of Korea and the People’sRepublic of China was written out according to the negotiation of practitioners on the basis of ‘Hoi Dam GiYo’ signed on October 3, 1962, and was the secret treaty composed of a preamble and five articles, and wasnot made public domestically and abroad, and was not registered on United Nations Secretariat. Based on NorthKorea-China Border Treaty concluded on October 12, 1962, North Korea-China Border Protocol was regulatedby harmoniously completing the missions to investigate the national border between both countries on the spot,set up its signposts, and attribute islands and sand islands in the national border rivers, and by clarifying thenational border between both countries, and by investigating its concrete locations. There is an opinion that it israrely possible to renegotiate these agreements after the unification between South and North Korea in light ofinternational law theories. However, there is a specific relationship between South and North Korea. That is,South and North Korea seem to be separate countries in the international society, whereas both maintain unitarystate in the subjectivity of both parties. Such phenomenon is especially typical if both parties aresimultaneously recognized by the third party. It follows from this situation that it is problematic whether NorthKorea whose stateness is not recognized by South Korea has its prestige as a treaty maker. About this problem,there is an opinion that, because North Korea has no treaty-making powers if North Korea’s stateness isrejected, the treaties concluded by North Korea are null and void, or an opinion that, because North Korea isin fact only a local regime which has no power to conclude the treaty representing entire Korea, the territorialtreaties related to entire Korea are invalid, or an opinion that, because North Korea is also an international lawsubject, it follows that North Korea has treaty-making powers and all the treaties concluded by North Korea areeffective. Therefore, the problem of succession is addressed on the premise that the treaties concluded by NorthKorea are valid. If they are null and void, such problem does not occur from the beginning. It follows that itis problematic whether, if they are effective, the general theories on state succession should or can be appliedbetween South and North Korea. In the end, even though Article 11 of the Vienna Convention on Successionof States in Respect of Treaties has the prestige of international custom, the succession problem of nationalborder in unified Korea can show its different succession formulas according to whether the unification formulasbetween South and North Korea are absorption, annexation, and merger or uniting of states. Also, in relation tomaritime boundary agreements, based on domestic literature or the literature acquired from China, some arguethat North Korea-China maritime boundaries were ascertained in North Korea-China Border Treaty. However,because North Korea-China Maritime Boundary Agreement has not yet been ascertained by North Korea orChina officially, indirect arguments or inferences based on several circumstances are possible, but it is not yetreasonable to affirm its existence firmly, Even if North Korea-China Maritime Boundary Agreement has beenalready concluded, because exclusive economic zone and continental shelf can not be regarded as the conceptidentical with national borders in land, unified Korea may need to renegotiate with China. Of course, althoughsome argue that Article 11 of the Vienna Convention should be also applied even to exclusive economic zoneor continental shelf except territorial sea, because such argument is not generally approved in terms of academictheories or in the interpretative aspect of that article, it is persuasive to limit the scope of maritime boundariesto territorial sea. Moreover, according to case laws, in Guinea-Bissau vs. Senegal case, the arbitral tribunalawarded that the legal principle of state succession and the principle of ‘uti possidetis’ should be also appliedto even maritime boundaries. However, it is unreasonable that this case is executed as a precedent. TheInternational Court of Justice also decided that the realization of such principles did not include maritimeboundaries. Furthermore, because territorial sea can not be identical with internal waters or lands in all theaspects, if the concept of territory stipulated by Article 12 is interpreted strictly, such scope of territoryexcludes territorial sea. In this case, unified Korea may need to renegotiate with China territorial sea as well asexclusive economic zone and continental shelf. In addition, in solving the succession problem of maritimeboundaries, the practices to handle the succession problem of treaties concluded with other countries by theformer Soviet Union remain as significant formulas.