A running motor for assisting an engine in driving a vehicle or singly driving the vehicle and an auxiliary unit motor for driving a compressor for an air conditioner are controlled by a common inverter via a changeover switch. According to this construction, the running motor and the auxiliary unit motor can be driven by the single inverter, and this can contribute to the reduction in the number of components, costs, space and weight, when compared with a case where inverters are provided to be used exclusively for the running motor and the auxiliary unit motor, respectively.