To prevent the edge fitting of the sliding surface of an outer ring and the sliding surface of an inner ring.

The sliding surface 1a of an outer ring 1 is positioned on a straight line passing a contact position Ca (Cb) and the spherical surface center O2 of an inner ring 2, and it is drawn in a recessed spherical surface with a radius r1 making a point Oa (Ob) set off at the reverse side to the contact position Ca (Cb) from the spherical surface center O2. When a thrust load Fa (Fb) is loaded, the sliding surface 1a of the outer ring 1 is angular contacted to the sliding surface 2a of the inner 2 at the contact position Ca (Cb) closer a distance L in the axial direction from the end face 1b (1c) at the reverse thrust load side to the bearing center Y side.