WHEEL BEARING DEVICE

PROBLEM TO BE SOLVED: To provide a wheel bearing device achieving a reduction in torque while securing a seal function.SOLUTION: In a hub unit 1 comprising an outer ring 2 fixed to a knuckle 20 and an inner ring 3 rotatably supported to the outer ring 2, a flange 3c formed protrusively toward the outside in the radial direction and attaching a wheel is formed at one end of the inner ring 3 in the axial direction, a seal member 7 fit to an end of an internal peripheral face at the flange 3c side of the outer ring 2 and constituting a bearing internal space 6 by sealing an annular space S1 between the outer ring and the inner ring 3 is arranged, and the seal member 7 has an annular lip 72d composed of an elastic body and continuously slide-contacting with a side face 3d of the flange 3c. In the lip 72d, a fastening margin of a portion arranged in the center part H1 set in a region in the vicinity of the center in the vertical direction in a state in which the hub unit 1 is mounted on a vehicle is set smaller than fastening margins of portions arranged in an upper part H2 set in a region above the center part H1 and in a lower part H3 set in a region below the center part H1.