To prevent the rotation in an inclined manner by fitting a sintered oil retaining bearing on either or each side of an inner ring or an outer ring of single row ball bearing.

A cylindrical sintered oil retaining bearing 4 is fitted into a space to be formed on a side part of an outer ring 2, a ball 3 and a retainer 5. The outside diameter of the sintered oil retaining bearing 4 is equal to the inside diameter of an outer ring sleeve 6, and the inside diameter is slightly larger than the outside diameter of an inner ring 1. Thus, the sintered oil retaining bearing 4 is fixedly fitted to the inside of the outer ring sleeve 6, and a small gap(g) is formed between the bearing and the outer circumferential surface of the inner ring 1. The gap(g) for suppressing the inclination is determined by the dimensions A and B so that the inclination does not exceed the allowable range. When the outer ring 2 side or the inner ring 1 side is inclined while a single composite bearing is in operation, one end of the B side of the oil sintered retaining bearing 4 is abutted on the A side of the inner ring 1 to prevent the shaft from being further inclined.