A hybrid power supply device which can properly control the operation of an engine generator and can prevent an increase in size of the system. The hybrid power supply device includes an engine generator and a capacitor, and comprises DC current bus bars to which the engine generator and the capacitor are connected in parallel and which supplies electric power to the outside, a boost converter connected between the DC current bus bars and the engine generator, and a controlling portion which controls the boost converter to regulate the electric power to be supplied from the engine generator to the DC current bus bars. Since electric power can be supplied to the outside not only from the engine generator but also from the capacitor, the engine generator can be made compact. By controlling the boost converter by the controlling portion, the electric power to be supplied to the DC current bus bars from the engine generator can be regulated, which suppresses a change in load of the engine generator with respect to a change in electric power to be supplied to the outside from the power supply device.