An output-power control apparatus which is provided in an electric power system connecting a secondary battery provided with a power converter for controlling electric charge/discharge and a power generator in parallel and controls a total output power as a total of output powers from a power generator and a secondary battery, the output-power control apparatus comprising: total-output-power-instruction output means for outputting a total-output-power instruction for controlling the total output power; power-generator-output-power detection means for detecting the output power from the power generator; secondary-battery-charge/discharge-power instruction calculation means (17D,19) for calculating a secondary-battery-charge/discharge power instruction for controlling an electric power to be charged to or discharged from the secondary battery, based on the total output power instruction output by the total-output- power-instruction output means and based on the output power from the power generator detected by the power-generator-output-power detection means; secondary battery control means for controlling the power converter, based on the secondary-battery-charge/discharge power instruction calculated by the secondary-battery-charge/discharge-power instruction calculation means (17D, 19); and characterised by further comprising: power-generator-output power limiting means for limiting the output power from the power generator to a smaller one of a total electric power and a rated output of the power generator by comparing the total electric power and the rated output of the power generator with each other, the total electric power being a total of the total output power depending on the total-output-power instruction which is output by the total-output-power-instruction output means and an electric power which is chargeable in the secondary battery. total-output-power-instruction output means for outputting a total-output-power instruction for controlling the total output power; power-generator-output-power detection means for detecting the output power from the power generator; secondary-battery-charge/discharge-power instruction calculation means (17D,19) for calculating a secondary-battery-charge/discharge power instruction for controlling an electric power to be charged to or discharged from the secondary battery, based on the total output power instruction output by the total-output- power-instruction output means and based on the output power from the power generator detected by the power-generator-output-power detection means; secondary battery control means for controlling the power converter, based on the secondary-battery-charge/discharge power instruction calculated by the secondary-battery-charge/discharge-power instruction calculation means (17D, 19); and characterised by further comprising: power-generator-output power limiting means for limiting the output power from the power generator to a smaller one of a total electric power and a rated output of the power generator by comparing the total electric power and the rated output of the power generator with each other, the total electric power being a total of the total output power depending on the total-output-power instruction which is output by the total-output-power-instruction output means and an electric power which is chargeable in the secondary battery.