Inexpensive heating fuel is used to generate heat required for completion of reformation of raw material to be reformed such as hydrocarbon gas, heavy oil or oil refining pitch so that the raw material may be reformed economically and stably. A reformer has a raw material feeder that feeds a predetermined amount of raw material to be reformed to a fluidized-bed reforming furnace; a fuel feeder feeds heating fuel to a fluidized-bed combustion furnace; and a controller regulates the fuel to be fed to the combustion furnace so as to impart heat to the circulating particles in the combustion furnace such that the raw material fed to the reforming furnace can be completely reformed in the reforming furnace.