NOVELTY - A hydrogen production apparatus (1, 1') comprises modification part (6) which produces hydrogen-containing reformed gas by modifying raw fuel and water vapor using a burner (10), shift reaction part (7) where shift reaction of reformed gas is performed and carbon monoxide concentration of reformed gas is reduced, 1st shift catalyst part (31) aligned with axis (G) of shift reaction part, 2nd shift catalyst part (32) surrounded by 1st shift catalyst part in accordance with axis of shift reaction part, reformed gas flow path (S1), and cooling unit (L1).    USE - A hydrogen production apparatus for fuel cell system (claimed).    ADVANTAGE - Performance improvement in hydrogen production apparatus and fuel cell system is achieved.    DETAILED DESCRIPTION - A hydrogen production apparatus (1, 1') comprises modification part (6) which produces hydrogen-containing reformed gas by modifying raw fuel and water vapor using a burner (10), shift reaction part (7) where shift reaction of reformed gas is performed and carbon monoxide concentration of reformed gas is reduced, 1st shift catalyst part (31) aligned with axis (G) of shift reaction part, 2nd shift catalyst part (32) surrounded by 1st shift catalyst part in accordance with axis of shift reaction part, reformed gas flow path (S1) which circulates reformed gas from one side of axial direction to the other side (31a) in the outer periphery part of shift reaction part, and cooling unit (L1). The 1st shift catalyst part leads reformed gas out from one edge part (31b) of an axial direction while introducing reformed gas to the other side edge part of an axial direction, while the 2nd shift catalyst part leads reformed gas out from the other side edge part of an axial direction while introducing reformed gas driven out from the 1st shift catalyst part from one edge part of an axial direction. An INDEPENDENT CLAIM is included for fuel cell system (100) comprising fuel cell stack (20) which produces electric power using reformed gas generated by hydrogen production apparatus (1, 1').    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of the front end view of a hydrogen production apparatus. (Drawing includes non-English language text).    Modification part (6)    Shift reaction part (7, 13)    Burner (10)    1st shift catalyst part (31)    2nd shift catalyst part (32)    Axis (G)