Abstract: An apparatus for driving a cutter holder in a machining tool include, a sleeve, a holder carrying rod, a cylinder body unit, a piston rod, and a spring unit. The sleeve and the cylinder body unit are adapted to be disposed on a machine bed, and are spaced apart from each other. The holder carrying rod is movable axially and reciprocally in the sleeve, and is adapted to carry the cutter holder thereon. The piston rod is aligned with the holder carrying rod, and can be activated to reciprocate in the cylinder body unit. When the piston rod moves forward in the cylinder body unit, it impels the holder carrying rod to move forward in the sleeve. When the piston rod moves rearward in the cylinder body unit, a spring unit biases the holder carrying rod to move rearward toward the piston rod. A tongue unit is mounted fixedly on the front end of the cylinder body unit, and engages an annular groove in the sleeve, thereby preventing axial movement of the sleeve relative to the cylinder body unit.