The article discusses the attitude of Japanese government towards the Treaty on the Prohibition of Nuclear Weapons (TPNW), which was introduced in the United Nations’ agenda in 2017. The case of Japan is special and even unique, due to the fact that, in spite of its historical experience of atomic bombings and the position of its civil society, which supports the idea of a nuclear ban, Tokyo refuses to sign the Treaty. Moreover, the rejection of the TPNW does not correlate with Japan’s active participation in the international nuclear non-proliferation initiatives. As far as Japan is undoubtedly an influential member of world community and a threshold state, possessing advanced nuclear technologies and ready to transform its peaceful nuclear program into a military one, its position regarding the TPNW can have a significant impact on the prospects of the nuclear non-proliferation regime in Asia. The author concludes that Japan has demonstrated an obvious refusal to sign the TPNW, in spite of all factors which could have produced the alternative position. However, its views remain ambiguous, as Tokyo adheres to international nuclear non-proliferation regimes and comprehensive nuclear disarmament. On the one hand, Japan is one of the U.S.’ main allies, remaining under the U.S. security guaranties, being protected by the U.S. nuclear umbrella from external threats, and incorporated in the global system of nuclear deterrence. On the other hand, there is certain support for ideas of nuclear non-proliferation and prohibition of nuclear weapons in Japanese society, which is demonstrated by the activity of Japanese anti-nuclear nongovernmental organizations. Consequently, in relation to the TPNW, Japan demonstrates an inconsistent course, involving the reliance on the U.S. nuclear umbrella in order to provide its security and active participation in the international nuclear non-proliferation initiatives simultaneously.