In forming an actuator, a large end surface of a tapered roller of a tapered roller bearing is shot with minute particles of silicon carbide having a diameter of 0.5 to 100 μm and having an angle formed by crushing, and such a surface is scraped concavely at a diameter within a range from 0.5 to 100 μm to form a large number of concavities having a depth of equal to or greater than 1 μm at a pitch of equal to or less than 200 μm. The concavities are non-continuous and isolated from each other, and serve as a lubricant puddle. The concavities are formed by scraping and not by plastic deformation, and thus the surface is not hardened.