The present invention provides a hub bearing, made of carbon steel for machine structural use, which has a long life even in a strict lubricating conditionby improving the resistance to peeling starting from the surface. A grease for the hub bearing contains abaseoil anda thickener, and in thebaseoil, thenumber of naphthenic carbons found by an n-d-M ring analyzing method accounts for 32 to 37% of a whole number of carbon atoms in the base oil. The base oil is a mineral oil or a mixed oil of a mineral oil and a synthetic hydrocarbon oil. The thickener is a urea compound shown by the following formula (1) and is contained at 1 to 40 mass % for the entire grease. The grease for the hub bearing is enclosed in the hub bearing. (In the formula (1) , R2 indicates an aromatic hydrocarbon group having 6 to 15 carbon atoms, and R1 and R3 indicate at least one hydrocarbon group selected from an alicyclic hydrocarbon group and an aromatic hydrocarbon group.)
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