A charge/discharge system comprising: a motor generator adapted to serve as a driving power source for driving a vehicle and perform electric power generation using power of the vehicle; a capacitor adapted to supply electric power to the motor generator and charge electric power generated by the motor generator; a secondary battery; an electric power converter adapted to complementarily perform charging and discharging between the capacitor and the secondary battery; and a controller adapted to control operations of the motor generator and the electric power converter, wherein the controller is adapted to control the electric power converter based on at least one of charging conditions of the capacitor and the secondary battery such that electric power charged in the capacitor is charged in the secondary battery, or the electric power charged in the secondary battery is charged in the capacitor, characterized in that the controller is adapted to obtain charging conditions of the capacitor and the secondary battery, and is further adapted to control the electric power converter such that the electric power charged in the secondary battery is charged in the capacitor when a charging capacity of the capacitor is lower than a first predetermined value, control the electric power converter such that the electric power charged in the capacitor is charged in the secondary battery when the charging capacity of the capacitor is higher than a second predetermined value, control the electric power converter such that the electric power charged in the capacitor is charged in a restricted manner to the secondary battery when the charging capacity of the secondary battery is higher than a third predetermined value, and control the electric power converter such that the electric power charged in the secondary battery is charged in a restricted manner to the capacitor when the charging capacity of the secondary battery is lower than a fourth predetermined value. a motor generator adapted to serve as a driving power source for driving a vehicle and perform electric power generation using power of the vehicle; a capacitor adapted to supply electric power to the motor generator and charge electric power generated by the motor generator; a secondary battery; an electric power converter adapted to complementarily perform charging and discharging between the capacitor and the secondary battery; and a controller adapted to control operations of the motor generator and the electric power converter, wherein the controller is adapted to control the electric power converter based on at least one of charging conditions of the capacitor and the secondary battery such that electric power charged in the capacitor is charged in the secondary battery, or the electric power charged in the secondary battery is charged in the capacitor, characterized in that the controller is adapted to obtain charging conditions of the capacitor and the secondary battery, and is further adapted to control the electric power converter such that the electric power charged in the secondary battery is charged in the capacitor when a charging capacity of the capacitor is lower than a first predetermined value, control the electric power converter such that the electric power charged in the capacitor is charged in the secondary battery when the charging capacity of the capacitor is higher than a second predetermined value, control the electric power converter such that the electric power charged in the capacitor is charged in a restricted manner to the secondary battery when the charging capacity of the secondary battery is higher than a third predetermined value, and control the electric power converter such that the electric power charged in the secondary battery is charged in a restricted manner to the capacitor when the charging capacity of the secondary battery is lower than a fourth predetermined value.