To provide a bearing unit for wheel which improves grease life by reducing an agitation resistance of grease by decreasing an amount of grease sealed within the bearing, and extending the bearing service life by suppressing temperature increase of the bearing by utilizing the grease efficiently.

A small diameter step section of a hub ring 2 includes a first small diameter step section 2b extending axially from an inner side rolling face 2a, and a second small diameter step section 2d which extends axially from this first small diameter step section 2b through a shoulder section 2c and allows an inner ring 3 to be press fitted thereto, wherein an annular wall member 12 is externally suitable for the first small diameter step section 2b with a fine radial clearance; this wall member 12 consists of thermoplastic synthetic resin; its width dimension A is set slightly larger by ΔA than the width dimension B of the first small diameter step section 2b; and the end surface 3b of the inner ring 3 is brought into contact with the shoulder section 2c of the hub ring 2 in such a condition that the wall member 12 is elastically deformed by ΔA when the inner ring 3 is press-fitted to the second small diameter step section 2d.

COPYRIGHT: (C)2010,JPO&INPIT