Awareness of the danger of nuclear proliferation began in Europe with the ratification of the Rapacki Plan in Poland. This growing awareness then spread to the rest of the world, including the Korean peninsula. At the end of the Cold War, Asia also acknowledged the seriousness of the threat to international security brought about by nuclear proliferation. In Northeast Asia, North Korea implemented a nuclear arms policy that highlighted the problem of proliferation. As a consequence, the US as well as neighboring countries felt obliged to negotiate the non-proliferation of nuclear weapons. However, these efforts have not yet succeeded. This evident lack of progress remains a puzzle. Why is Northeast Asia unable to sign a treaty for the creation of a nuclear-weapon-free zone (NWFZ) as in other regions? What is the specific situation in Northeast Asia? What can Northeast Asia learn from the five treaties that have already been successfully negotiated?