[en] Regulation of nuclear fuel materials in Japan is outlined. Nuclear materials should be regulated in order to restrict their use in peaceful use and to prohibit their transfer to weapons in addition to safety regulation as radioactive materials. The Science and Technology Agency is in charge of the regulation of nuclear materials (nuclear raw materials and nuclear fuel materials) in Japan. International trend in the regulation of nuclear materials is explained with emphasis on the Treaty on Non-Proliferation of Nuclear Weapons (NPT), the safeguard and nuclear material protection. The number of facilities in Japan which are objects of IAEA safeguard are indicated.(T.H.)