A hub unit is fixed to a body's side in such a state that a lubricating
ring member is held between a hub receiving surface which constitutes a
step portion of a large-diameter portion and a vehicle inner side end
face of an inner ring with at least either of an abutment surface of the
lubricating ring member with the hub receiving surface and an abutment
surface thereof with the vehicle inner end face of the inner ring made to
constitute a lubricant holding surface which holds a lubricant, whereby
the hub receiving surface and the vehicle inner side end face of the
inner ring are made to easily slip relative to each other, thereby making
it possible to prevent the generation of an abnormal noise between
contact surfaces of the inner ring and the hub receiving surface of the
axle.