Thread cutting device for sewing machine

The utility model discloses a thread cutting device of a sewing machine, with positive thread cutting operation and easy regulation of the position of a thread cutting knife. The thread cutting device of a sewing machine comprises a base plate fixedly arranged on a sewing machine, a swing rod pivoted on the base plate, and a thread cutting knife tackle which can be linked by the swing rod. The thread cutting knife tackle is provided with a knife feeding element which can move on the base plate, and a cutting knife blade which is overlapped with the knife feeding element and linked with the swing rod. The back end part of the knife feeding element of the thread cutting knife tackle is formed with a pin joint groove and provided with a guide element which is convexly arranged inside a back guide groove of the cutting knife element for guiding.