NOVELTY - A hydrogen production apparatus has modifier (11), a shift reaction portion (12) and a selective oxidation reaction portion. The selective oxidation reaction portion is provided with a selective oxidation catalyst layer containing selective oxidation catalyst. An oxygen-absorbent layer (21) containing oxygen absorbent is laminated below a selective oxidation catalyst layer. The oxygen absorbing agnet absorbs oxygen, and is regenerated by a reducing gas. The hydrogen production apparatus further has a unit to release air (BB) from the downstream of oxygen absorbent layer.    USE - For manufacturing hydrogen-containing gas used as fuel for fuel cell of fuel cell system (claimed) used as electric power generating apparatus used for motor vehicles, fixed electric power generation system and co-generation system.    ADVANTAGE - The hydrogen production apparatus reliably prevents oxidation degradation of catalyst within the hydrogen production apparatus, even when start-up and shutdown are repeated without conducting purge operation.    DETAILED DESCRIPTION - A hydrogen production apparatus has modifier (11), a shift reaction portion (12) and a selective oxidation reaction portion. The modifier generates hydrogen-containing gas by modification reaction of raw material for hydrogen production. The shift reaction portion reduces carbon monoxide concentration in the outlet gas of the modification portion, by shift reaction. The selective oxidation reaction portion is provided with a selective oxidation catalyst layer containing selective oxidation catalyst. The selective oxidation catalyst selectively oxidizes carbon monoxide to further reduce carbon monoxide concentration in the outlet gas of the shift reaction portion. An oxygen-absorbent layer (21) containing oxygen absorbent is laminated below a selective oxidation catalyst layer. The oxygen absorbing agent absorbs oxygen, and is regenerated by a reducing gas. The hydrogen production apparatus further has a unit to release air (BB) from the down stream of the oxygen absorbent layer. The oxygen absorbent contains metal chosen from ruthenium, platinum, gold, nickel, cobalt, rhodium, palladium, iridium, silver and rhenium, and oxide chosen from ceria, zirconia, titania, yttria, manganese oxide, stannic oxide, iron oxide, copper oxide and zinc oxide. An INDEPENDENT CLAIM is included for operating method of fuel cell system.    DESCRIPTION OF DRAWING(S) - The figures show the flowchart of outline of hydrogen production apparatus. (Drawing includes non-English text)    Modifier (11)    Shift reaction device (12)    Oxygen absorbent layer (21)    Valves (101-103)    Air (BB)