NOVELTY - A hydrogen generating apparatus (1) has a modification portion (20) for producing a hydrogen-containing gas by reforming reaction of a raw material and water vapor, a modification temperature detecting portion (21), a transformation portion (25), a combustion portion (2), a detecting portion for determining appropriate detected value of portion (21), and an operation control portion (16). The portion (16) determines appropriate detected value of portion (21) based on measured value when operation of combustion portion is controlled based on detected temperature.    USE - Hydrogen generating apparatus is used for fuel cell electric power generation system (claimed).    ADVANTAGE - The apparatus enables to produce hydrogen-containing gas with low carbon monoxide concentration, and has excellent reliability.    DETAILED DESCRIPTION - A hydrogen generating apparatus has a modification portion for producing a hydrogen-containing gas by reforming reaction of a raw material and water vapor, a modification temperature detecting portion, a transformation portion, a combustion portion for supplying heat for reforming reaction, a detecting portion for determining appropriate detected value of modification temperature detecting portion, and an operation control portion (16). The portion (16) determines appropriate detected value of modification temperature detecting portion based on measured value of detection portion when operation of combustion portion is controlled based on detected modification temperature. The transformation portion has a transformation catalyst for reaction of carbon monoxide and water vapor in hydrogen-containing gas. An INDEPENDENT CLAIM is included for fuel cell electric power generation system (100).    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of fuel cell electric power generation system. (Drawing includes non-English language text)    Hydrogen generating apparatus (1)    Combustion portion (2)    Operation control portion (16)    Combustion air supply portion (18)    Modification portion (20)    Modification temperature detecting portion (21)    Transformation portion (25)    Fuel cell electric power generation system (100)