A roller bearing having spacers interposed between rollers is provided. During operation of the bearing, the spacers are prevented from being pressed by adjacent rollers against an inner ring or inner ring, so that heat generation and wear of the spacers at a guiding surface are reduced. The roller bearing includes an outer ring, an inner ring, a plurality of rollers, and a plurality of spacers interposed between adjacent rollers. Surfaces of each spacer that face respective rolling contact surfaces of the rollers each have a concave shape that extends across a pitch circle of the rollers, and the spacers are guided by one of the outer and inner rings. When each of the spacers is held between the adjacent rollers, a clearance is formed between the one of the outer and inner rings and the spacer.