NOVELTY - A fuel cell electric power generation system (100) comprises a modifier (30), a modification temperature detecting portion (21), a fuel cell, a combustion portion (2), a combustion detecting portion (22) and an operation-control portion (16). The modifier generates hydrogen-containing gas by performing modification reaction of raw material and water vapor. The modification temperature detecting portion detects the reaction temperature of modification reaction. The hydrogen-containing gas and oxygen-containing gas are supplied into fuel cell.    USE - Fuel cell electric power generation system.    ADVANTAGE - The fuel cell electric power generation system has excellent operation stability. The change in flow volume of combustion air is analyzed easily from the reaction temperature detected by modification temperature detecting portion, and without using sensor such as off-gas flow element and combustion-air flow element.    DETAILED DESCRIPTION - A fuel cell electric power generation system comprises a modifier, a modification temperature detecting portion, a fuel cell, a combustion portion, a combustion detecting portion and an operation-control portion. The modifier generates hydrogen-containing gas by performing modification reaction of raw material and water vapor. The modification temperature detecting portion detects the reaction temperature of modification reaction. The hydrogen-containing gas and oxygen-containing gas are supplied into fuel cell. The combustion portion is equipped with a combustion-air supply portion of combustion air, the hydrogen-containing gas returned from the fuel cell is burnt, and a heat required for modification reaction is supplied. The combustion detecting portion detects the ionic-current value of the flame in combustion portion. The operation-control portion analyze whether the operation of combustion-air supply portion is appropriate to the ionic-current value detected by combustion detecting portion.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic block diagram of fuel cell electric power generation system.    Hydrogen generating apparatus (1)    Combustion portion (2)    Fuel cell (8)    Operation-control portion (16)    Modification temperature detecting portion (21)    Combustion detecting portion (22)    Modifier (30)    Fuel cell electric power generation system (100)