A bearing apparatus for a wheel of vehicle comprising: - an outer member formed on its inner circumferential surface with double row outer raceway surfaces ; - an inner member including a hub wheel having a wheel mounting flange formed integrally therewith at one end thereof, hub bolts being adapted to be mounted on the wheel mounting flange equidistantly along its outer periphery, one inner raceway surface formed on the outer circumferential surface thereof oppositely to one of the double row outer raceway surfaces and a cylindrical portion axially extending from the inner raceway surface , and including an inner ring press fitted on the cylindrical portion and formed on its outer circumferential surface with the other inner raceway surface opposite to the other raceway surface of the double row outer raceway surfaces ; and - double row groups of balls freely rollably contained between the outer raceway surfaces and inner raceway surfaces respectively of the outer member and the inner members , wherein a pitch circle diameter (PCDo) of the ball group of the outer side is larger than a pitch circle diameter (PCDi) of the ball group of the inner side, characterized in that - ribs are formed on a surface of the inner side of the wheel mounting flange , each rib being formed by an outline including straight portions radially extending outward from the base of the wheel mounting flange and a rounded tip portion having a predetermined radius of curvature (r) centered on the axial center of hub bolt and substantially corresponding to a distance between the axial center and the outermost periphery of the wheel mounting flange , - a substantially conical recess is formed in an outer side end portion of the hub wheel , and - a substantially constant wall thickness is formed between the conical recess and the outer circumferential surface of the hub wheel of the outer side end portion thereof. - an outer member formed on its inner circumferential surface with double row outer raceway surfaces ; - an inner member including a hub wheel having a wheel mounting flange formed integrally therewith at one end thereof, hub bolts being adapted to be mounted on the wheel mounting flange equidistantly along its outer periphery, one inner raceway surface formed on the outer circumferential surface thereof oppositely to one of the double row outer raceway surfaces and a cylindrical portion axially extending from the inner raceway surface , and including an inner ring press fitted on the cylindrical portion and formed on its outer circumferential surface with the other inner raceway surface opposite to the other raceway surface of the double row outer raceway surfaces ; and - double row groups of balls freely rollably contained between the outer raceway surfaces and inner raceway surfaces respectively of the outer member and the inner members , wherein a pitch circle diameter (PCDo) of the ball group of the outer side is larger than a pitch circle diameter (PCDi) of the ball group of the inner side, characterized in that - ribs are formed on a surface of the inner side of the wheel mounting flange , each rib being formed by an outline including straight portions radially extending outward from the base of the wheel mounting flange and a rounded tip portion having a predetermined radius of curvature (r) centered on the axial center of hub bolt and substantially corresponding to a distance between the axial center and the outermost periphery of the wheel mounting flange , - a substantially conical recess is formed in an outer side end portion of the hub wheel , and - a substantially constant wall thickness is formed between the conical recess and the outer circumferential surface of the hub wheel of the outer side end portion thereof. <EOS>