A system controller 100 controlling an electric power generation system of a fuel cell powered vehicle realizes functions as a fuel-cell power-generation response time estimation section 101, by which power-generation response time of a fuel cell 1 is estimated, an optimum motor-output response time estimation section 102, by which an optimum output response time of a drive motor 22 is estimated, and a motor-output response time control section 103 for controlling an output response time of the drive motor 22. The power-generation response time of the fuel cell is estimated based on an atmospheric pressure detected by an atmospheric sensor 35 and depending on this power-generation response time, the output response time of the drive motor is controlled so as to limit a rate of change in a torque command value for the drive motor such that the output response time of the drive motor is not shorter than power-generation response time of the fuel cell.