An annular sensor holder (5) has an axial end (15) including a protrusion (18). The axial end (15) is fitted in a circumferential groove (7), such as a seal groove, of a bearing race (2) fitted to a stationary member (9) so that the sensor holder (5) can slide in the circumferential direction relative to the bearing race (2). In this state, the sensor holder (5) is coupled to the stationary member (9) by a fixing arrangement (19). Thus, when the bearing race (2) creeps, the sensor holder (5) slides relative to the bearing race (2) and does not rotate relative to the stationary member (9). This prevents breakage of connecting wires.