The invention is a belt tightening drive for tightening a seat belt that can be wound about a winding shaft, comprising a spindle shaft driven by a drive unit and a worm drive with a worm supported in a torque-proof fashion on the spindle shaft and a driven wheel, engaged therewith and supported in a torque-proof fashion on the winding shaft. According to the invention it is provided that the worm comprises a first toothed section with a first toothed geometry, wherein the first position of the worm the first toothed section engages the driven wheel, the worm comprises at least a first toothed section and following a second toothed section with a second toothed geometry, with the first and second toothed geometries being embodied differently.