<p>A ball screw having a lubricant oil feeder constructed so as not to allow the lubricating oil in a ball rolling groove to leak outside. A ball screw having a lubricating oil feeding mechanism installed at the shaft end of a nut, and a seal disposed outside the same, wherein the lubricating oil feeding mechanism has an applicator (31) with its front end held in slide contact with the ball rolling groove (11a), it being arranged that the lubricating oil is fed to the ball rolling groove (11a) through the applicator (31), and an oil lip (32) with its front end held in slide contact with the surface of the ball rolling groove (11a) is installed in the vicinity of the applicator (31) with a predetermined spacing (D) defined between the oil lip and the applicator (31).</p>
