A direct drive motor module has hollow disk-like plates (21, 22) for interconnecting the rotation side of an in-wheel motor (3) and a wheel (2) and a drive force transmission mechanism (20) comprising cross guides (23) for guiding the plates (21, 22) in the vertical direction. To mount the direct drive motor module to the wheel (2), attachment holes (2s) are formed in the spoke portions of the wheel (2), the fixing portions of connection pins (30) having a spherical pin head which is a mating portion are fitted in the attachment holes (2s), guide holes (40) having a predetermined clearance relative to the outer diameter of the pin head (33) are formed in the wheel side plate (22) supporting the wheel (2) sides of the cross guides (23), the pin heads of the connection pins (30) are mated with the guide holes (40), and the direct drive motor module is mounted to the wheel (2). The direct drive motor module can be reliably mounted to the wheel (2) even if assembly accuracy is not so high.