Enhanced fretting resistance, high-speed capability, and service live are achieved by a roller bearing comprised of a plurality of rolling elements held between inner and outer races with a cage interposed therebetween, and wherein oil film of lubricating oil of which the dynamic viscosity at 40° C. is 20 to 150 mm2/s, and which preferably contains an extreme pressure agent and a corrosion preventing agent, is formed on the raceway surfaces of the inner and outer races, the cage and the rolling elements and grease is enclosed.