An axle bearing apparatus includes a hub shaft including a wheel-mounting flange formed at its outer end portion, and a cylindrical portion formed on an inner side surface of the flange, a bearing portion press-fitted on the cylindrical portion of the hub shaft and including an inner ring, an outer ring and rolling elements disposed between the inner and outer rings, and a slinger having a through hole formed through its central portion. The through hole is fitted on the cylindrical portion such that an outer diameter of the slinger is generally equal to an outer diameter of the flange, and the slinger is press-clamped to the inner side surface of the flange by bolts press-fitted respectively in a plurality of bolt holes formed in the flange. O-rings are interposed between the flange and the slinger.