A belt-buckle tightener for a seat belt system in a vehicle, having: a rotatable spindle which is connected to a belt buckle via a draw-in cable; and a drive for rotation of the spindle, as a result of which the draw-in cable is rolled up on the spindle and the belt buckle is moved in the tightening direction, and the drive being integrated in the spindle. Integration of the drive in the spindle reduces the structural space required. In addition, the number of individual parts which are required is reduced since, inter alia, a separate driving spindle is not required. Rather, the spindle for winding up the draw-in cable at the same time forms the driving spindle.