In this power output apparatus, an operation line lower in torque than the maximum torque line is adopted as a reference operation line for moving the motor operating point along the reference operation line in a steady state, and for controlling the motor operating point such that the power output from the motor becomes the required power by increasing the motor torque while substantially maintaining the motor rotation speed irrespective of the reference operation line when the power required of the motor increases. Therefore, according to this power output apparatus, even when the power required of the motor increases suddenly, the motor torque increases without increasing the motor rotation speed and the power output from the motor becomes equal to the required power immediately.