A front end portion of an output shaft is supported by a bearing mounted to an inner peripheral surface of a partition that separates a power distributing planetary gear and a speed change unit. A rear end portion of the output shaft is supported via a bearing which is interposed along a portion of the same plane along which also lies a mounting surface of a bearing in a rear wall that supports a rear end portion of a rotor of a second motor. As a result, the output shaft is supported by a twin support structure via the bearings by the partition and the rear wall.