To realize a structure in a low cost, capable of preventing surely the rotation of a sensor carrier relative to a housing, in spite of use in a long period on a place where vibration is given.

The base end part of an locking pin 17a is supported and fixed on an end face in the axial direction of an outer ring 1. The middle part of the locking pin 17a is inserted into a through hole 32 formed on a part of a cover 23 composing a sensor carrier 10a. Besides, the head part of the locking pin 17a is engaged with an engaging hole 33 formed on an engaging collar part 30 installed on the housing 14a side. As a result, the rotation of the sensor carrier 10a is surely prevented, and the disconnection of a harness 13 can be surely prevented.