This article explores the double-standard approaches of U.S. nonproliferation policy. Since the advent of Nuclear Nonproliferation Regime, the U.S. has been devoted itself to prevent nuclear proliferation. In order to achieve its goal, the U.S. has been used the methods of nonproliferation and counterproliferation. Despite regime's continuous efforts, the nuclear proliferation occurred and is continuing by new proliferators. There are a number of competing variables for explaining why the proliferation process is still ongoing and the global institutions and rules do not work well. This paper insists that the failure of the regime is caused by several factors including the U.S. double-standard approach against proliferators. To explain the U.S. nuclear policy and its adaptation on each proliferation cases, this paper used Glenn Chafetz and HESO' cases which analyze the relationships between nuclear proliferation and economic sanctions since 1970s. As a result, this article found that the U.S nuclear policy has a double standard in terms of its adaptation against proliferators. The reasons are explained by the limitations of sanctions and characteristics of U.S. political culture. In conclusion, Korea should prepare the possibility of changing U.S. nuclear policy to North Korea.