A vehicle wheel bearing apparatus has a wheel hub integrally formed with a peripheral wheel mounting flange at one end and a double row rolling bearing. The double row rolling bearing has an outer member integrally formed with a peripheral body mounting flange and with double row outer raceway surfaces. An inner member, including the wheel hub, is formed with double row inner raceway surfaces each arranged opposite to each of the double row outer surfaces. Double row rolling elements are freely rotatably contained between the double row outer and inner raceway surfaces. The double row rolling bearing is adapted to receive a predetermined preload. A separate outer or inner ring is arranged on at least one of the outer or inner members. A preload varying mechanism is arranged at an abutting portion between the outer and inner members to vary the preload applied to the bearing. The preload varying mechanism can be extended or contracted based on an output signal from a detecting sensor to detect the vehicle running conditions.