Abstract: A cylindrical roller bearing with synthetic resin cages, in which heat generation of the bearing during high speed rotation is suppressed, while sufficient rigidity and strength is secured, so that the bearing is excellent in high speed performance. The cylindrical roller bearing (10) has synthetic resin cages (20) each including an annular portion (21) disposed in one axial end portion of the cage (20), and a plurality of columnar portions (25) extending from a side surface of the annular portion (21). The minimum inner diameter d1 of the annular portion (21) is set to be smaller than the maximum inner diameter d2 of each columnar portion (25), and the inner diameter of the columnar portion (25) is set to be equal to the inner diameter d1 of the annular portion (21) over a range of length not longer than ? of the whole length of the columnar portion (25).