To reduce the radial dimension of a cylinder drum by connecting bearings of a motor to the cylinder drum and a support part in the radial direction, and arranging the bearings between the cylinder drum and a bearing bush surrounding the cylinder drum.

A motor has a stationary support 1. This support part 1 is formed to be fixed to a constituent member fixed to a vehicle, and connected to a bearing bush 2. A driven part 4 is supported in the bearing bush 2 in the radial direction using two bearings 3a, 3b formed as inclined rolling bearings arranged in O-shape. The driven part 4 is mainly composed of a cylinder drum 5 of the motor. A wheel flange 5a and a rim centering means 5b are integrally formed at the cylinder drum 5. With the cylinder drum 5 thus supported outside in the bearing bush 2, the motor can be formed reducing radial dimention, and weight can also be reduced. Dynamical improvement is therefore attained, and the critical value of rotating speed can be remarkably heightened.