NOVELTY - Main water-vapor generator (11) provided at exit side of modification catalyst (9) of reaction device (5), feeds water vapor to inlet side of catalyst. Auxiliary combustion chamber (31) provided at outer side of device, has burner (41) and heat exchanger which pre-heats air/hydrocarbon fuel fed to device. Pipe supplies water to heat exchanger, so that produced water vapor is fed to device, during device start-up.    USE - For producing hydrogen for use in fuel cell system with fuel cell having polymeric electrolyte, which is used for electric power generation.    ADVANTAGE - Enables efficiently producing hydrogen at the start-up of the hydrogen manufacturing apparatus, even when the main water-vapor generator has not reached water-vapor generation temperature, by use of the heat exchanger which heats water, and produces water vapor. Enables quickly and easily starting the hydrogen manufacturing apparatus. Hence, stabilizes the reformed-gas inlet-side temperature of carbon monoxide shift reaction catalyst.    DETAILED DESCRIPTION - Pipes are provided for supplying water to the main water-vapor generator and the heat exchanger. INDEPENDENT CLAIMS are also included for:    (a) starting method of hydrogen manufacturing apparatus which involves igniting the burner, and pre-heating air or hydrocarbon fuel to be supplied to the catalyst, using the heat exchanger. Water is supplied to the heat exchanger, and is heated and converted into water vapor. Water vapor is supplied to the reaction device. Subsequently, water is supplied to the main water-vapor generator, so that water vapor produced from the main generator is fed to the reaction device; and    (b) operating method of hydrogen manufacturing apparatus, which involves controlling the supply amount of water to the main generator and the heat exchanger, based on the drive load of the hydrogen manufacturing apparatus.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the fuel cell system with the hydrogen manufacturing apparatus. (Drawing includes non-English language text).    reaction device (5)    modification catalyst (9)    main water-vapor generator (11)    auxiliary combustion camber (31)    burner (41)