A diameter dimension of a chamfer 11 which is formed on axial end faces of a cylindrical roller 8 which is retained in each pocket 7 of a cage 2 whose axial positioning is realized by a roller guide at a portion which lies closer to an outside diameter side thereof is made such that a central flat surface 9 which lies on an inside diameter side of the chamfer 11 is not exposed from an external surface of an outside diameter side flat plate portion 14. Then, a difference between a minimum value ΔB of an amount by which the cylindrical roller 8 projects from the external surface of the outside diameter side flat plate portion 14 and a dimension W11 of the chamfer 11 with respect to a diameter direction thereof is made smaller than a thickness T2 of the cage 2.