A cylindrical roller bearing comprising: an outer ring having an outer ring raceway surface formed on an inner circumferential surface thereof; an inner ring having an inner ring raceway surface formed on an outer circumferential surface thereof and having a pair of flange portions at both axial end portions of the inner ring raceway surface; a plurality of cylindrical rollers rollably arranged between the outer ring raceway surface and the inner ring raceway surface; and a cage made of resin and having a pair of circular ring portions and a plurality of column portions connecting the pair of circular ring portions in an axial direction, the cage forming a plurality of pocket portions that rotatably hold the plurality of cylindrical rollers respectively, wherein a single recessed groove is formed in an inner wall surface of each of the pair of circular ring portions forming the pocket portion, the recessed groove facing at least a center point of a roller end surface of the cylindrical roller and open from an inner circumferential surface to an outer circumferential surface of the circular ring portion, wherein the recessed groove is spaced apart in a circumferential direction from a pocket corner portion between the circular ring portion and the column portion, and wherein the recessed groove is formed such that a circumferential width thereof is equal from an outer circumferential side end surface to an inner circumferential side end surface thereof, or a circumferential width at the outer circumferential side end surface thereof is larger than a circumferential width at the inner circumferential side end surface thereof, characterized in that when the circumferential width of the recessed groove at the outer circumferential side end surface is M, a roller diameter of the cylindrical roller is D, a height of the flange portion is H, and a circumferential pocket clearance is ΔP, M - ΔP ≤ D - H and 0.2 × D ≤ M - ΔP are satisfied. an outer ring having an outer ring raceway surface formed on an inner circumferential surface thereof; an inner ring having an inner ring raceway surface formed on an outer circumferential surface thereof and having a pair of flange portions at both axial end portions of the inner ring raceway surface; a plurality of cylindrical rollers rollably arranged between the outer ring raceway surface and the inner ring raceway surface; and a cage made of resin and having a pair of circular ring portions and a plurality of column portions connecting the pair of circular ring portions in an axial direction, the cage forming a plurality of pocket portions that rotatably hold the plurality of cylindrical rollers respectively, wherein a single recessed groove is formed in an inner wall surface of each of the pair of circular ring portions forming the pocket portion, the recessed groove facing at least a center point of a roller end surface of the cylindrical roller and open from an inner circumferential surface to an outer circumferential surface of the circular ring portion, wherein the recessed groove is spaced apart in a circumferential direction from a pocket corner portion between the circular ring portion and the column portion, and wherein the recessed groove is formed such that a circumferential width thereof is equal from an outer circumferential side end surface to an inner circumferential side end surface thereof, or a circumferential width at the outer circumferential side end surface thereof is larger than a circumferential width at the inner circumferential side end surface thereof, characterized in that when the circumferential width of the recessed groove at the outer circumferential side end surface is M, a roller diameter of the cylindrical roller is D, a height of the flange portion is H, and a circumferential pocket clearance is ΔP, M - ΔP ≤ D - H and 0.2 × D ≤ M - ΔP are satisfied.