An overview of the present status of development of fusion nuclear technologies at Japan Atomic Energy Research Institute is presented. A tritium handling system for the ITER was designed, and the technology for each component of this system was demonstrated successfully. An ultraviolet laser with a wavelength of 193 nm was found quite effective for removing tritium from in-vessel components of D-T fusion reactors. Blanket technologies have been developed for the test blanket module of the ITER and for advanced blankets for DEMO reactors. This blanket is composed of ceramic Li2TiO3 breeder pebbles and neutron multiplier beryllium pebbles, whose diameter ranges from 0.2 to 2 mm, contained in a box structure made of a reduced-activation ferritic steel, F82H. Mechanical properties of F82H under a thermal neutron irradiation at up to 50 displacements per atom (dpa) were obtained in a temperature range from 200 to 500°C. Design of the International Fusion Materials Irradiation Facility (IFMIF) has been developed to obtain engineering data for candidate materials for DEMO reactors under a simulated fusion neutron irradiation up to 100 to 200 dpa, and basic development of the key technologies to construct the IFMIF is now under way as an International Energy Agency international collaboration.