Abstract: A thread-cutting device for a cyclically operated double lock stitch sewing machine forming part of an automatic sewing system serves to cut the needle and bobbin or looper threads, respectively, at the underside of the throat or stitch plate of the sewing machine in close proximity to the needle hole in the throat or stitch plate. For cutting of the threads, a cutting edge is moved with respect to a stationary cutting blade into a cutting position for simultaneously cutting of the two threads. The carrier for the movable cutting tool moves the stationary cutting blade into its effective cutting position and further carries thread control fingers which assist in preparing the threads for the cutting operation. The cutting mechanism is actuated by the control means for the cyclically operated double lock stitch sewing machine.