To simplify the constitution of a thread cutter and assembly work, and to improve a thread cutting performance by increasing the blade pressure of an upper blade member and a lower blade member when cutting a thread.

Of the upper blade member 21 and the lower blade member 22 provided in the thread cutter 20, a thread handing member 27 roughly in a chevron shape in the plane view is disposed near the upper surface of the upper blade member 21, the upper blade member 21 is fixed to an upper blade main body part 21a by a fixing machine screw 28 at the proximal end side fixing part 27a, and the distal end of the blade forming part 21b of the upper blade member 21 is elastically energized downwards by a thread handling part 27b extended from the proximal end side fixing part and positioned near the upper side of the blade forming part 21b. Thus, a prescribed blade pressure is generated between the upper blade 21c of the upper blade member 21 and the lower blade 22a of the lower blade member 22, and a bobbin thread and a core thread extended from the sewing end position of working cloth are surely cut.