An in-wheel motor system, wherein the rotating side case 3b of an in-wheel motor 3 is connected to a wheel 2 by a flexible coupling 10 comprising a plurality of hollow disk-like plates 11A to 11C and direct-acting guides 12A and 12B, the non-rotating side case 3a of the motor 3 is connected to a knuckle 5 by a damping mechanism 20 for connecting the non-rotating side case 3a of the motor to the knuckle 5 which is a frame dress-up part of the vehicle, comprising two plates 26 and 27 whose moving directions are limited to the vertical direction of the vehicle by direct-acting guides 21 and which are interconnected by first spring elements 22 which move in the vertical direction of the vehicle and dampers 25 with a spring element, each comprising a damper 23 and a second spring element connected to the damper 23 in series and arranged parallel to the first spring elements 22, whereby the drive force of the in-wheel motor 3 can be transmitted to the wheel 2 without fail and the road holding properties of a vehicle can be further improved by greatly reducing variations in the ground-contact load of a tire.