Abstract: A ball screw with a dust-proof and lubricating device comprises: a screw, a nut, a plurality of balls, an oil-absorbing member, a return unit, and two dust-proof members. The nut includes an axial oil-guiding hole, a plurality of radial oil holes in communication with the oil-guiding hole and the helical groove of the nut, and an oil-feeding hole in communication with one of the radial oil holes. The oil-absorbing member is disposed in the oil-guiding hole and the radial oil holes. The return unit is disposed in the nut to enable the turning and circulation of the balls. The two dust-proof members are located at both ends of the axial hole. The ball screw can still be lubricated when it is disposed in a vertical position, and the dust-proof and lubricating device which won't add axial length to the nut.