A wear detection probe is provided to cushion an impact from a rotor to the wear detection probe and to hold the wear detection probe in a specified position during the contact with the rotor. For these purposes, a biasing mount plate 16 is formed with biasing pieces 21. A stopper mount plate 15 is formed with stopper pieces 19, and a wear detection probe 10 is provided with locking pins 14. When being subjected to an impact from a rotor R, the wear detection probe 10 moves backward while the biasing pieces 21 undergo an elastic deformation by being pushed by the locking pins 14, with the result that the impact is cushioned. When the wear detection probe 10 moves backward, the locking pins 14 come into contact with the stopper pieces 19 and, accordingly, the wear detection probe 10 is held in contact with the rotor R while being held in the specified position.