Bearing device for wheel

A wheel bearing apparatus includes a roller bearing, an inner shaft having an outer circumferential surface to which an inner ring of the roller bearing is installed, a coupler ring attached to an end portion of the inner shaft, and a caulked portion provided in an end portion of the inner shaft so as to fix the coupler ring and the roller bearing to the inner shaft so as to be immovable in an axial direction of the inner shaft. An outer diameter of the coupler ring is set smaller than a diameter of a shoulder portion of the inner ring. Alternatively, a protruding portion is provided in any one of opposing end surfaces of the coupler ring and the inner ring, whereby the coupler ring is arranged away from a seal member. Accordingly, it is possible to avoid an interference of the coupler ring with the seal member.