A fuel cell power generation system of the invention includes a hydrogen supply unit for reforming hydrocarbon fuel to generate reformed gas including hydrogen or generating reaction gas including the hydrogen from a hydrogen material, an oxygen supply unit, a fuel cell for receiving the hydrogen from the hydrogen supply unit and oxygen from the oxygen supply unit, for power generation, temperature sensors each for detecting a temperature of the hydrogen supply unit, and a temperature control unit for adjusting generated power, thereby controlling the temperature of the hydrogen supply unit, based on the detected temperature. The temperature control unit includes a target power setting unit for setting first and second target powers as generated power target values, and a target power switching unit for performing target value switching between the first and second target powers according to a predetermined change in the detected temperature.