NOVELTY - Hydrogen gas production apparatus has heating unit (40) and reaction units (10,20,30). Units (10,20) dehydrogenate fuel using dehydrogenation catalyst (a,b) heated at temperature (t1,t2), respectively, by heating unit. Unit (30) contains dehydrogenation and hydrogenation catalyst (c), and carries out dehydrogenation and hydrogenation of fuel by contacting with catalyst (c) in absence and presence of hydrogen, respectively.    USE - For producing hydrogen gas used as fuel for fuel cell used as power supply for vehicle.    ADVANTAGE - The hydrogen gas production apparatus enables to produce hydrogen gas with favorable thermal efficiency, and has reduced size.    DETAILED DESCRIPTION - Hydrogen gas production apparatus has a heating unit and reaction units (10,20,30). The heating unit heats the exterior by inserting heating atmosphere from one side to other side. The unit (10) carries out dehydrogenation of fuel under pressure using a dehydrogenation catalyst (a) heated at temperature (t1) by heating unit. The unit (20) carries out dehydrogenation of fuel using a dehydrogenation catalyst (b) heated at temperature (t2) less than temperature (t1) by heating unit, and is provided at insertion direction downstream side of heating atmosphere of unit (10). The unit (30) is provided at insertion direction downstream side of heating atmosphere of unit (20), and contains dehydrogenation and hydrogenation catalyst (c). The unit (30) carries out dehydrogenation of fuel contacting with catalyst (c) in absence of hydrogen, and hydrogenation of resulting dehydrogenated fuel contacting with catalyst (c) in presence of hydrogen gas. The catalyst (c) is heated at temperature (t3) less than temperature (t2) by heating unit, during dehydrogenation and hydrogenation.    DESCRIPTION OF DRAWING(S) - The figure shows the outline perspective view of reactor.    reaction units (10,20,30)    finned-tube type water-cooled cooler (15)    partition plate for cooling (11)    air supply tube (30a)    heater (40)