An
electric motor 10 and a reduction gear mechanism 11 are connected to each other by a flexible
coupling 12, such as an Oldham's
coupling, which is a
power transmission mechanism. Also, a casing 11c of the reduction gear mechanism 11 is integrally structured together with a
knuckle 5, which is an unsprung part of a vehicle, or mounted to the
knuckle 5. Further, a motor case 10a of the
electric motor 10 is mounted to a motor mounting member 4m provided on the lower part of a strut 4 for suspending the
knuckle 5 through the medium of a shock absorbing mechanism 20 equipped with a spring member 21, a
damper, and two guide members 23 for guiding the operating direction of the spring member 21 and the
damper. An in-wheel
motor system thus structured allows the
mass of the motor 10 to act as the
mass of a dynamic
damper and thus features not only improved
ground contact performance and riding comfort of a vehicle running on a rough road but also superior space efficiency.