In a power output apparatus of the present invention, a control unit sets a WOT (wide open throttle) line L2, where the maximum torque of an engine attains, as a boundary between an over drive area and an under drive area in the case where a rotor shaft of an assist motor is set in a state of over drive linkage. The control unit determines a target working point of an outer rotor shaft of a clutch motor, which functions as a drive shaft, based on an externally required output, and selects the WOT line L2 as a performance line of the engine in the case where the target working point of the outer rotor shaft is present in the under drive area. The control unit then sets a switching instruction flag, in order to change the state of linkage of the rotor shaft of the assist motor from the state of over drive linkage to a state of under drive linkage. This arrangement of the invention reduces the maximum load capacity of the assist motor and decreases the maximum electric current of an inverter circuit for driving the assist motor.