To provide a bearing device for a wheel with a built-in in-wheel motor, capable of reducing a space in an axial direction while ensuring lighter weight and rigidity of the bearing device for a wheel.

In the bearing device, a hub ring 13 and a bearing case 14 are formed of an aluminum alloy by die casting. An output member 6 constituting a decelerator 3 includes: a connecting shaft 35 which is inserted into the hub ring 13 on the outer circumference of the shaft via a serration; an annular base part 37 formed with a large diameter at the inner side of the connecting shaft; and a holding part 54 comprising a pair of flanges 38, 39 which are disposed to protrude outward in a radial direction from the annular base part and to oppose to each other in an axial direction, and in which a pinion gear 32 is housed, and a bridge 40 axially connecting the flanges to each other. The side face 54a of the holding part 54 of the output member 6 comes in contact with the larger end face 21a of an inner ring 21 in a directly butted state, and the output member 6 is fixed to the hub ring 13 to be capable of transmitting torque, by a fixing nut 36 screwed to the end of the connecting shaft 35.