A bearing unit which comprises a bearing main body and a balancer. The bearing main body includes an inner ring member which is fixed to one end of an output shaft of a drive source and which has its axis eccentric with respect to an axis of the output shaft, an outer ring member whose diameter is larger than that of the inner ring member, and a plurality of rolling elements interposed between the inner ring member and the outer ring member. The balancer is formed integrally with the inner ring member in a direction in which an axis of the output shaft is eccentric with respect to an axis of the inner ring member and corrects dynamic unbalance caused by an eccentric movement of the bearing main body together with the rotation of the output shaft.