A wheel bearing apparatus incorporating a wheel speed detecting apparatus has an outer member (4) with an integrally formed body mounting flange (4b) and double row outer raceway surfaces (4a) formed on the inner circumferential surface of the outer member (4). An inner member (3) includes a wheel hub (1) with an integrally formed wheel mounting flange (7) at one end. A cylindrical portion (1b) axially extends from the wheel mounting flange (7). An inner ring (6) is fitted on the cylindrical portion (1b) of the wheel hub (1). Double row inner raceway surfaces (1a, 6a) are formed on the outer circumferential surfaces of the wheel hub (1) and inner ring (6), respectively opposite to the double row outer raceway surfaces (4a). Double row rolling elements (5) are rotatably arranged between the outer and inner raceway surfaces (4a; 1a, 6a). An encoder (19) is mounted on the outer circumferential surface of the inner ring (6). An annular sensor holder (15) is arranged on the end of the outer member (4) opposite to the encoder (19). A wheel speed detecting sensor (20) is integrally molded with the sensor holder (15) and arranged opposite to the encoder (19), via a predetermined radial gap. The encoder (19) has an annular ring configuration and its characteristics alternately and equidistantly vary along its circumferential direction. A seal is arranged at the inboard side of the encoder (19). The seal includes first and second annular sealing plates (21, 22) mounted on the sensor holder (15) and the inner ring (6), respectively, and opposite toward each other. The encoder (19) is mounted on the second sealing plate (22).