The cooling apparatus uses oil to cool an electric motor whose output is transmitted to a drive shaft inserted into a motor shaft via a reduction gear and a differential gear. An oil seal seals the gap between the differential case of the differential gear and the outer peripheral surface of the drive shaft. An oil passage is formed inside the drive shaft. An oil introduction hole is formed in the drive shaft on the side of the differential gear with respect to the oil seal to introduce oil from the differential gear into the in-drive-shaft oil passage. An oil outlet hole is formed in the drive shaft on the side of the electric motor with respect to the oil seal to draw oil from the in-drive-shaft oil passage to the inside of the motor shaft.