To provide a wheel bearing for preventing damage to a multipole magnet even when foreign matters are biten between the multipole magnet as a magnetic encoder and a magnetic sensor.

The wheel bearing comprises an inward member 1 and an outward member 2, a plurality of rollers 3 stored between the inward and outward members, and a sealing device 5 for sealing a circular space at its end between the inward and outward members 1, 2. The sealing device 5 has first and second circular sealing plates 11, 12 mounted on mutually different members out of the inward member 1 and the outward member 2. Both sealing plates 11, 12 are formed in sectionally L-shape with respective cylindrical portions 11a, 12a and vertical plate portions 11b, 12b and opposed to each other. The first sealing plate 11 is fitted to the rotation-side member out of the inward member 1 and the outward member 2. The multipole magnet 14 having magnetic poles alternately formed in the peripheral direction is mounted on the vertical plate portion 11b. The outward side of the multipole magnet 14 is covered with a non-magnetic protecting plate 18.