The invention discloses a worm tightening device and belongs to the technical field of machine tool equipment. The worm tightening device is provided in order to solve the problem that a special tightening device is not available for worms processed by a cold rolling technology. The worm tightening device provided by the invention comprises a right tightening device and a left tightening device, wherein the right tightening device comprises a centre sleeve, the centre sleeve is in a shape of a hollow shaft, and an inner hole of the centre sleeve comprises a large-diameter section close to a worm and a small-diameter section far from the worm; a first locating sleeve is fixed in the small-diameter section of the centre sleeve; the end surface close to the worm of the centre sleeve is fixedwith a first shaft sleeve through bolts; a first rotating shaft is fixed in the first shaft sleeve through a bearing, and the first rotating shaft is of a hollow structure; one end of a first locatingrod is fixed in the first locating sleeve through a first spring, and the other end of the first locating rod extends into an inner cavity of the first rotating shaft; a second locating rod is further arranged in the inner cavity of the first rotating shaft, one end of the second locating rod is pressed against the first locating rod, and the other end of the second locating rod is pressed against the worm; and the structure of the left tightening device is similar to that of the right tightening device. The worm tightening device is convenient to use and ensures worm processing precision.