A rotation sensor assembly includes an encoder, mounted on one end of an inner member of a bearing, and a rotation sensor fitted to one end of an outer member of the bearing in face-to-face relation with the encoder. A cylindrical wall of a core metal of the encoder press-fitted onto the inner member has a cylindrical extension protruding axially outwardly from one end of the cylindrical wall. A displacement sensor assembly includes a pair of displacement sensors provided in face-to-face relation with the cylindrical extension and spaced equidistantly from each other in a circumferential direction. The rotation sensor is positioned between the displacement sensors in the circumferential direction.