<p>A wheel bearing apparatus provided with a wheel rotational speed detector which has a simplified L-shape and is constituted by a detector end portion and a circuit housing (20) perpendicular to the detector end portion. The detector end portion contains a sensor in opposition to a detected member fixed to an rotating inside member (1) of the wheel bearing and is embedded in an outside member (7) of the wheel bearing, while the circuit housing (20) contains a circuit (19) for processing a signal input from the sensor (16) and is mounted on an outside surface of the outside member (7) in parallel with the axial direction of the outside member (7) so that the circuit housing (20) is inside in the radial direction of outside surface of a flange (6) provided for the inside member (1).</p>
