NOVELTY - A desulfurizer (1) of the hydrogen production apparatus, contains desulfurizing agent for decreasing concentration of sulfur content in hydrogen production raw material. The desulfurizing agent is zeolite type. During stop state of the apparatus, the inlet and exit line of the desulfurizer are closed in a state with temperature more than the atmospheric temperature of the desulfurizing agent.    USE - For hydrogen production apparatus used in fuel cell system which is used for moving motor vehicle, cogeneration system, industrial and noncommercial electric power generation system.    ADVANTAGE - The method enables stable driving without impairing the zeolite type desulfurizing agent.    DETAILED DESCRIPTION - The hydrogen production apparatus has a modifier (21) for modifying the desulfurized raw material for hydrogen production and to manufacture hydrogen containing gas. INDEPENDENT CLAIMS are also included for the following:    (1) operation method of hydrogen production apparatus involves opening the exit line of desulfurizer, so that the pressure of the desulfurizer exists in the range of plus minus 10 kPa-G, when starting the hydrogen production apparatus. The desulfurizer has layer which contains zeolite type desulfurizing agent (3) and the metal type desulfurizing agent (4) inside of a container with respect to the flow direction of raw material. The metal type desulfurizing agent is selected from copper, cobalt, nickel. Both the desulfurizing agents are held at same temperature. The raw material for hydrogen production is natural gas or liquefied petroleum gas;    (2) stop method for fuel cell system which uses hydrogen containing gas obtained from hydrogen production apparatus as fuel; and    (3) operation method of fuel cell system.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the fuel cell system.    desulfurizer (1)    zeolite type desulfurizing agent (3)    metal type desulfurizing agent (4)    modifier (21)    burner (21a)    hot water storage tank (25)