Method for measuring axial force of a bearing device

There is disclosed a bearing device in which a double row angular contact ball bearing is mounted to an outer periphery of a hub wheel, a caulking portion is bent diametrically outward and caulked on an end face of an inner ring of a bearing, thereby preventing the bearing from falling out from the bearing device and to applying a pre-load to the bearing. An axially outer edge of the inner ring is chamfered roundly, the caulking portion is provided at its shaft end with a small-diameter portion, and a starting point of the small-diameter portion is located closer to an axially central portion than a chamfer-starting point of the axially outer edge of the inner ring.