A charge/discharge system capable of supplying electric power to an electric motor generator and of charging with regenerative electric power from the electric motor generator, comprising: a capacitor connected to the electric motor generator; a secondary battery connected in parallel to the capacitor; an electric power converter placed between the capacitor and the secondary battery to increase/decrease charge/discharge voltage of the secondary battery; and a controller to control the electric power converter, wherein the controller includes: a request power calculation unit configured to calculate request input/output power for the electric motor generator based on current and voltage of the capacitor and input/output current of the electric power converter; a capacitor discharging bias factor map configured to specify a ratio of electric power to be supplied from the capacitor to the electric motor generator to the request input power calculated by the request power calculation unit, based on the SOC of the capacitor; a capacitor charging bias factor map configured to specify a ratio of electric power to be stored in the capacitor from the electric motor generator to the request output power calculated by the request power calculation unit, based on the SOC of the capacitor; and a subtraction unit configured to calculate charge/discharge power of the secondary battery by subtracting, from the request input/output power, the charge/discharge power of the capacitor obtained from the capacitor discharging bias factor map or the capacitor charging bias factor map, characterized in that, the capacitor performs charge/discharge with the electric motor generator only, and no charge/discharge is performed between the capacitor and the secondary battery. a capacitor connected to the electric motor generator; a secondary battery connected in parallel to the capacitor; an electric power converter placed between the capacitor and the secondary battery to increase/decrease charge/discharge voltage of the secondary battery; and a controller to control the electric power converter, wherein the controller includes: a request power calculation unit configured to calculate request input/output power for the electric motor generator based on current and voltage of the capacitor and input/output current of the electric power converter; a capacitor discharging bias factor map configured to specify a ratio of electric power to be supplied from the capacitor to the electric motor generator to the request input power calculated by the request power calculation unit, based on the SOC of the capacitor; a capacitor charging bias factor map configured to specify a ratio of electric power to be stored in the capacitor from the electric motor generator to the request output power calculated by the request power calculation unit, based on the SOC of the capacitor; and a subtraction unit configured to calculate charge/discharge power of the secondary battery by subtracting, from the request input/output power, the charge/discharge power of the capacitor obtained from the capacitor discharging bias factor map or the capacitor charging bias factor map, characterized in that, the capacitor performs charge/discharge with the electric motor generator only, and no charge/discharge is performed between the capacitor and the secondary battery. a request power calculation unit configured to calculate request input/output power for the electric motor generator based on current and voltage of the capacitor and input/output current of the electric power converter; a capacitor discharging bias factor map configured to specify a ratio of electric power to be supplied from the capacitor to the electric motor generator to the request input power calculated by the request power calculation unit, based on the SOC of the capacitor; a capacitor charging bias factor map configured to specify a ratio of electric power to be stored in the capacitor from the electric motor generator to the request output power calculated by the request power calculation unit, based on the SOC of the capacitor; and a subtraction unit configured to calculate charge/discharge power of the secondary battery by subtracting, from the request input/output power, the charge/discharge power of the capacitor obtained from the capacitor discharging bias factor map or the capacitor charging bias factor map, characterized in that, the capacitor performs charge/discharge with the electric motor generator only, and no charge/discharge is performed between the capacitor and the secondary battery.