The invention relates to a ball screw driving structure for a numerically-controlled machine tool. The ball screw driving structure for the numerically-controlled machine tool is innovatively characterized by comprising a bearing seat, a transmission case, a ball screw and a motor, the bearing seat is fixed at one end of a machine tool base, the transmission case is fixed at the other end of the machine tool base, the left end of the ball screw is supported in the bearing seat through a bearing pack A, the right end of the ball screw is supported in the transmission case through a bearing pack B, the motor is mounted on a motor mounting hole of the transmission case, and an output shaft of the motor is connected with the right end of the ball screw through a coupler. The ball screw driving structure for the numerically-controlled machine tool has the advantages that the ball screw driving structure is applicable to medium-speed rotating and high-precision use conditions as one end of the ball screw is fixed while the other end of the ball screw is movable; and the bearing pack B is axially limited by the aid of a pressing ring, an inner ring lock nut, an inner ring limit step of the ball screw and the transmission case step face, axial clearance is reduced beneficially, and transmission and positioning precision is high.