To provide a protective device for a wheel speed sensor which can simplify constitution and reduce manufacturing cost.

A housing 14 covering the entire circumference of a tone wheel 11 is integrally formed on a trailing arm, a proximity sensor 18 is provided at the housing 14 opposing the tone wheel 11, and a projecting part 20 is provided on the upstream side in the forward rotational direction of the tone wheel 11 of the proximity sensor 18. A cover part 22 covering the projecting range of the proximity sensor 18 is provided, a projecting part 24 is provided on the downstream side so that foreign matters such as pebbles entering the housing 14 collides the projecting parts 20 and 24 and are ejected outside the housing 14 without impacting the proximity sensor 18.