The International Thermonuclear Experimental Reactor (ITER) is an experimental thermonuclear tokamak reactor that will test basic technologies of physics. The conceptual design activity of ITER required joint international work at the Max Plank Institute for Plasma Physics in the Garching Germany from 1988 to 1990. The proposals from Japan were summarized by the Fusion Experimental Reactor (FER) Team and the Superconducting Magnet Laboratory, both of the Japan Atomic Energy Research Institute (JAERI). This paper describes the Japanese contributions to the design concepts of the magnet system for ITER. The concepts of a magnet system design originated from the test data from the Large Coil Task and the Demo Poloidal Coil programs at JAERI. Most of design concepts are adapted for an option of the ITER Magnet design. The differences between Japanese design and the other designs will be analyzed using experimental results. (author).