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, characterized in that, the controller controls so that, if SOC of the secondary battery is equal to or greater than a preset first setting value, regenerative electric power of the electric motor generator is stored in the capacitor only, and if SOC of the secondary battery falls below the first setting value, a part or an entire of the regenerative electric power of the electric motor generator is stored in the secondary battery, 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; and a capacitor charging 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 secondary battery, wherein the capacitor charging factor map is configured so that, as the SOC of the secondary battery falls below the first setting value and decreases, an amount of electric power to be stored in the secondary battery increases. 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, characterized in that, the controller controls so that, if SOC of the secondary battery is equal to or greater than a preset first setting value, regenerative electric power of the electric motor generator is stored in the capacitor only, and if SOC of the secondary battery falls below the first setting value, a part or an entire of the regenerative electric power of the electric motor generator is stored in the secondary battery, 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; and a capacitor charging 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 secondary battery, wherein 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; and a capacitor charging 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 secondary battery, wherein the capacitor charging factor map is configured so that, as the SOC of the secondary battery falls below the first setting value and decreases, an amount of electric power to be stored in the secondary battery increases.