A chain guide configured to be arranged along a portion of an outer periphery of a timing chain, and comprising: a guide base elongated in a moving direction of the timing chain and including side plates; a plurality of roller shafts spaced apart from each other in a length direction of the side plates and each having two ends supported by the respective side plates; and rollers rotatably mounted on the respective roller shafts and configured to guide the chain, wherein each of the rollers is a roller bearing comprising: an outer race formed with flanges inwardly extending from respective axial ends of the outer race; a retainer mounted in the outer race and formed with pockets spaced apart from each other in a circumferential direction of the retainer; and roller elements received in the respective pockets and capable of rolling on a roller element rolling surface formed on an inner periphery of the outer race and on a cylindrical outer peripheral surface of a corresponding one of the roller shafts, characterized in that in each of the roller bearings, the retainer has a radially outer surface kept out of contact with the roller element rolling surface of the outer race, and a radially inner surface kept out of contact with the cylindrical outer peripheral surface, and wherein the roller elements are guided by the retainer, and the flanges of the outer race have an inner diameter (d 1) larger than a diameter (d 2) of circular contact portions between the retainer and the roller elements, and smaller than an outer diameter (D 1) of the retainer at outer ends of the retainer. a guide base elongated in a moving direction of the timing chain and including side plates; a plurality of roller shafts spaced apart from each other in a length direction of the side plates and each having two ends supported by the respective side plates; and rollers rotatably mounted on the respective roller shafts and configured to guide the chain, wherein each of the rollers is a roller bearing comprising: an outer race formed with flanges inwardly extending from respective axial ends of the outer race; a retainer mounted in the outer race and formed with pockets spaced apart from each other in a circumferential direction of the retainer; and roller elements received in the respective pockets and capable of rolling on a roller element rolling surface formed on an inner periphery of the outer race and on a cylindrical outer peripheral surface of a corresponding one of the roller shafts, characterized in that in each of the roller bearings, the retainer has a radially outer surface kept out of contact with the roller element rolling surface of the outer race, and a radially inner surface kept out of contact with the cylindrical outer peripheral surface, and wherein the roller elements are guided by the retainer, and the flanges of the outer race have an inner diameter (d 1) larger than a diameter (d 2) of circular contact portions between the retainer and the roller elements, and smaller than an outer diameter (D 1) of the retainer at outer ends of the retainer. an outer race formed with flanges inwardly extending from respective axial ends of the outer race; a retainer mounted in the outer race and formed with pockets spaced apart from each other in a circumferential direction of the retainer; and roller elements received in the respective pockets and capable of rolling on a roller element rolling surface formed on an inner periphery of the outer race and on a cylindrical outer peripheral surface of a corresponding one of the roller shafts, characterized in that in each of the roller bearings, the retainer has a radially outer surface kept out of contact with the roller element rolling surface of the outer race, and a radially inner surface kept out of contact with the cylindrical outer peripheral surface, and wherein the roller elements are guided by the retainer, and the flanges of the outer race have an inner diameter (d 1) larger than a diameter (d 2) of circular contact portions between the retainer and the roller elements, and smaller than an outer diameter (D 1) of the retainer at outer ends of the retainer.