The Japanese contribution to the construction of the ITER superconducting magnet system is to procure 25% of the toroidal field (TF) conductors, about half of the TF coil winding packs, all of the TF coil structures and all of the central solenoid conductors. The Japan Atomic Energy Agency has started extensive technology development for the preparation of these procurements. These include (1) trial fabrication of the superconductors at industry level and their performance demonstration, (2) manufacturing studies on the TF coil winding pack and structures, (3) full scale trial fabrication of TF coil structures and (4) the establishment of a database on the structural materials. All these activities are performed in close collaboration with Japanese industry involving around 20 major companies. Fruitful results have so far been obtained, although further development of the technology is required in some areas, including the qualification of conductors and the establishment of welding procedures of structures.