Abstract: A wheel bearing apparatus incorporating a rotational speed detecting apparatus has an outer member, an inner member and double row rolling elements contained between inner and outer raceway surfaces of the inner and outer members. A pulser ring is fit onto the outer circumference of the inner ring. A cylindrical sensor cap is fit into the inner circumference of the inner-side end of the outer member. A mounting portion axially projects from a radially outer portion of the sensor cap. An inserting bore is formed in the mounting portion so that it axially extends at a position corresponding to the pulser ring. A sensor unit is mounted in the inserting bore. A rotational speed sensor is embedded in the sensor unit to oppose the pulser ring, via a predetermined axial air gap. The position of a gate of a mold is set on the mounting portion of the sensor cap.