Abstract: A thread-cutting device for zigzag sewing machines for forming uniformly short thread ends regardless of the top stitch position of the last stitch. The thread cutter 28 is movable in a plane that is parallel to the thread catcher 33 and is connected by a drive unit 45 through 58 having stop sections 54, 55 to the drive of the thread catcher 33 such that the thread catcher can be moved, together with the cutter, into the cutting position located below the center of the stitch hole. While the thread cutter 28 stops in the cutting position, the thread catcher completes the thread separation process. The thread cutter 28 is moved back during the return movement of the thread catcher 33 only after the threads have been cut. The drive unit 45 through 58 for the thread cutter 28 is of positive-locking design, as a result of which even thick threads are cut reliably. The thread cutting device is particularly suitabloe for installation (even subsequent installation) in stitch group zigzag sewing machines.