A roller bearing, comprising: a first raceway member that has a raceway surface and a first rib that is positioned at one side of the raceway surface in an axial direction of the roller bearing; a second raceway member that has a raceway surface; a plurality of rollers arranged between the raceway surface of the first raceway member and the raceway surface of the second raceway member; and a plurality of separators (7; 107) which are arranged between the raceway surface of the first raceway member and the raceway surface of the second raceway member and each of which is interposed between two of the rollers next to each other in a circumferential direction of the first raceway member, wherein a first end surface (51; 151) of the separator (7; 107) that is one end surface of the separator (7; 107) in the circumferential direction has a first concave surface (31; 131) on which the roller slides, a first groove (41; 141) that is contiguous with the first concave surface (31; 131), and a second groove (61; 91, 92) that opens toward the first raceway member in the radial direction and wherein the first groove (41; 141) opens toward the first rib in the axial direction and opens toward the raceway surface of the first raceway member in a radial direction of the roller bearing, wherein the first groove (41; 141) and the second groove (61; 91, 92) are present only in a region that is on one side, in the radial direction, with respect to a position (80; 180) in the radial direction of the separator at which the roller contacts the first concave surface (31; 131) and at which the first concave surface (31; 131) is deepest in a depth direction of the first concave surface (31; 131), the first groove (41; 141) and the second groove (61; 91, 92) are formed by recessing the first concave surface (31; 131); and the first groove (41; 141) and the second groove (61; 91, 92) extend in the radial direction of the cylindrical roller bearing; characterized in that the first groove (41; 141) and the second groove (61; 91, 92) differ from each other in length in the radial direction of the cylindrical roller bearing. a first raceway member that has a raceway surface and a first rib that is positioned at one side of the raceway surface in an axial direction of the roller bearing; a second raceway member that has a raceway surface; a plurality of rollers arranged between the raceway surface of the first raceway member and the raceway surface of the second raceway member; and a plurality of separators (7; 107) which are arranged between the raceway surface of the first raceway member and the raceway surface of the second raceway member and each of which is interposed between two of the rollers next to each other in a circumferential direction of the first raceway member, wherein a first end surface (51; 151) of the separator (7; 107) that is one end surface of the separator (7; 107) in the circumferential direction has a first concave surface (31; 131) on which the roller slides, a first groove (41; 141) that is contiguous with the first concave surface (31; 131), and a second groove (61; 91, 92) that opens toward the first raceway member in the radial direction and wherein the first groove (41; 141) opens toward the first rib in the axial direction and opens toward the raceway surface of the first raceway member in a radial direction of the roller bearing, wherein the first groove (41; 141) and the second groove (61; 91, 92) are present only in a region that is on one side, in the radial direction, with respect to a position (80; 180) in the radial direction of the separator at which the roller contacts the first concave surface (31; 131) and at which the first concave surface (31; 131) is deepest in a depth direction of the first concave surface (31; 131), the first groove (41; 141) and the second groove (61; 91, 92) are formed by recessing the first concave surface (31; 131); and the first groove (41; 141) and the second groove (61; 91, 92) extend in the radial direction of the cylindrical roller bearing; characterized in that the first groove (41; 141) and the second groove (61; 91, 92) differ from each other in length in the radial direction of the cylindrical roller bearing.