Provided is a coal gasifier enabling a reduction in size of a shift reactor by generating hydrogen-rich gasified coal gas. In a coal gasifier (G) generating gasified coal gas by a gasification reaction proceeding in a furnace fed with a gasifiable raw material, such as coal, and a gasifying agent, at least one of water and steam is fed to the furnace as a material accelerating a hydrogen-generating reaction that proceeds simultaneously with the gasification reaction.