An IC tag 23 is fixed to a central portion of an axially outer end portion
face of a hub 10a which is a rotational ring which makes up the wheel
supporting bearing unit 5a. Historical information of the wheel
supporting bearing unit 5a is stored in the IC tag 23. The historical
information stored in the IC tag 23 can be read easily by the use of an
external device 28. Due to this, the traceability of the wheel supporting
bearing unit 5a can be increased.