To provide a hub unit bearing with an end cap having strong force of fixing itself to an outer ring and high sealing performance even when omitting an O-ring on an abutting portion between the outer ring and the end cap.

In the hub unit bearing, a second cylindrical portion of a core metal is protruded from the body of the end cap which is integrally formed with the synthetic resin body and the steel core metal, to the axial outer end, and fitted to the inner peripheral face of the outer ring to form a synthetic resin layer in part of the outer peripheral face of the second cylindrical portion in a range from an annular portion. The synthetic resin layer has a plurality of annular protruded portions arranged side by side on the outer periphery in the axial direction to form contact seal portions between the annular protruded portion and the inner peripheral face of the outer ring.

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