In an in-wheel motor driving device, since an involute speed reduction gear with a small difference in number of teeth which can be made small in size can be disposed on an inner side of an inner rotor type motor, a size of the in-wheel motor driving device in the direction of a rotational axis can be reduced. Further, in the inner rotor type motor, since a first stator is disposed so as to face a radially outer side of a large-diameter rotor, heat generated in the first stator is easily dissipated. On the other hand, in an outer rotor type motor, since a second stator is disposed so as to face a radially inner side of a small-diameter rotor, a torque radius of the small-diameter rotor can be made large, thereby making it possible to ensure a large torque capacity. Because of this, the outer rotor type motor can be made smaller in diameter than the inner rotor type motor, thereby making it possible to ensure a large space within a wheel.