A cooling apparatus of a dynamoelectric machine including a rotor and stator, wherein the dynamoelectric machine is mounted on a vehicle in a manner that an axial line of rotation thereof is oriented in a height direction of the vehicle. The cooling apparatus includes a hydraulic power source, a discharge port provided over a circumferential direction toward a space above a winding of the stator, a case configured in which the rotor and the stator are accommodated, and a coolant oil passage formed in the case so as to lead a coolant oil supplied from the hydraulic power source to the discharge port.