Abstract: A method for polishing a ball screw comprising a screw shaft defining a screw axis. The screw shaft is formed with a screw groove. The method comprises the steps of: rotating the screw shaft at a rotational speed about the screw axis; conveying a polishing tape having a polishing portion traveled around an outer peripheral surface of a pressing roller, the press roller being configured to rotate about a rotational axis; guiding the polishing tape such that the polishing portion is traveled around the outer peripheral surface; pressing the polishing portion against the screw groove; tilting the pressing roller such that the rotational axis is aligned with a lead angle; oscillating the pressing roller linearly along the rotational axis; moving the polishing tape at a moving speed in a direction parallel to the screw axis; and synchronizing the rotational speed with the moving speed based on a lead.