[en] The present status and plan of research and development on hydrogen production with High Temperature Gas-cooled Reactor (HTGR) were described in the report as well as development of technologies of nuclear reactor and gas turbine for HTGR. The HTGR has characteristics of high economy even small size, high safety and various utilization such as hydrogen production, electricity generation with high efficiency, process steam and district heating. IS process for producing hydrogen is one of thermochemical methods to split water with heat. Carbon doxide is not emitted to the environment by using the IS process. The HTGR system with IS process is an energy cycle of hydrogen and water. A cogeneration HTGR system named GTHTR300C, which supplies electricity, hydrogen and heat, can contribute to reduction of carbon dioxide. The GTHTR300C is expected in the world to be one of the most promising next generation nuclear plants (Generation IV systems) against global warming. (author)