To provide a speed detective bearing device which is simple and easy to replace the detective part.

In the speed detective bearing device, a fitting hole 2 of an annular resin member 5 disposed adjacent to a seal ring 3 is a separate item from a magnetic sensor 24 of a magnetic detector 23. The magnetic sensor 24 is detachably fitted to the fitting hole 22 of the plastic annular member 5. Accordingly, the magnetic sensor 24 can be exchanged independent of the seal ring 3, hence, the magnetic sensor 24 can be simply and easily exchanged. Further, since the inside wall of the fitting hole 2 is made of resin, the magnetic sensor 24 is not damaged in fitting.