A hollow shaft in which an externally threaded portion is forced on an outer periphery of an opening portion at one end of a main body and an engageable groove engageable with a tongue piece of a washer for a bearing is recessedly provided in the axial direction in the externally threaded portion. The engageable groove is recessedly provided to define a remaining wall portion at an outer end of the hollow shaft in the axial direction, whereby a reinforcing ring portion is integrally formed at an outer end portion of the externally threaded portion in the axial direction, the width of the remaining wall portion being set at such a dimension that the washer for the bearing can be coupled into the externally threaded portion.
