To reduce the size of a bearing device having a sealing device and a rotating speed detector by reducing an installation space for the sealing device and the rotating speed detector in the axial direction.

The sealing device 7 disposed between inner and outer ring members 24 and 21 rotated relative to each other is formed in a pack seal having two annular bodies 71 and 72 combined with each other. The pulsar ring 81 of the rotating speed detector 8 is installed on a second annular body 72 installed in the rotation side member 24 of the inner and outer ring members. The sensor 82 of the rotating speed detector 8 is detachably stored in a through- hole 21a provided in the fixed side member 21 of the inner and outer ring members in an area opposed radially to the pulsar ring 81. A window 71f for facing the sensor 82 to the pulsar ring 81 is provided at the installation portion of the first annular body 71.