NOVELTY - A hydrogen generating apparatus (100) comprises combustor which burns combustible gas, combustion exhaust gas flow path (50) which pours combustion exhaust gas emitted with combustor, modifier which generates hydrogen-containing-gas by reforming reaction from source gas, 1st modification-catalyst layer (1) which modifies source gas, 2nd modification-catalyst layer (2) which modifies source gas arranged in downstream of flow of source gas of 1st modification-catalyst layer, and 1st combustion exhaust gas flow path which is arranged at the part which adjoins 1st modification-catalyst layer.    USE - A hydrogen generating apparatus for fuel cell system (claimed).    ADVANTAGE - Apparatus costs low and has small size.    DETAILED DESCRIPTION - A hydrogen generating apparatus (100) comprises combustor which burns combustible gas, combustion exhaust gas flow path (50) which pours combustion exhaust gas emitted with combustor, modifier which generates hydrogen-containing-gas by reforming reaction from source gas, 1st modification-catalyst layer (1) which modifies source gas, 2nd modification-catalyst layer (2) which modifies source gas arranged in downstream of flow of source gas of 1st modification-catalyst layer, 1st combustion exhaust gas flow path which is arranged at the part which adjoins 1st modification-catalyst layer, and 2nd combustion exhaust gas flow path which is arranged at the part which adjoins 2nd modification-catalyst layer. Heat exchange amount of wall surface of 1st modification-catalyst layer side of 1st combustion exhaust gas flow path and combustion exhaust gas is larger than heat exchange amount of wall surface of 2nd modification-catalyst layer side of 2nd combustion exhaust gas flow path and combustion exhaust gas. An INDEPENDENT CLAIM is included for a fuel cell system comprising fuel cell electric-power-generated using hydrogen-containing-gas supplied from hydrogen generating apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic block diagram of the hydrogen generating apparatus. (Drawing includes non-English language text).    1st modification-catalyst layer (1)    2nd modification-catalyst layer (2)    Burner (5)    Combustion exhaust gas flow path (50)    Hydrogen generating apparatus (100)