To provide a hybrid power supply device capable of properly controlling an operation of an engine generator and also preventing the device from increasing in size.The power supply device including an engine generator 11 and a capacitor 15 comprises: a DC bus La having the engine generator 11 and the capacitor 15 connected in parallel and supplying electric power to an outside; a step-up converter 13 provided between the DC bus La and the engine generator 11; and a control section 17 controlling the step-up converter 13 and regulating electric power supplied from the engine generator 11 to the DC bus La. Since both of the engine generator 11 and the capacitor 15 can supply electric power to the outside, the engine generator 11 can be downsized. If the control section 17 controls the step-up converter 13, the electric power supplied from the engine generator 11 to the DC bus La can be regulated, and therefore, a load variation of the engine generator 11 can be suppressed to a variation of electric power supplied from the power supply device to the outside.