A high frequency surgical instrument having a forceps assembly at a fore distal end of an elongated insertion member, the forceps assembly being constituted by a pair of opening and closing grasper members which are shaped with a series of saw teeth on an inner meeting side in such a way that saw tooth portions on the two grasper members are at least partly brought into abutting engagement with each other when the grasper member are closed. For manipulating opening and closing actions of the grasper members, a manipulative transmission means is threaded through the insertion member, connecting the paired grasper members of the forceps to a manipulation handle which is attached to a proximal end of the insertion member. Each one of the grasper members is formed of a conducting material and arranged to have a width narrower than outside diameter of the insertion member on the saw-toothed inner side. The grasper members are electrically connectible to a high frequency power source, and are entirely covered with an insulating coat except saw tooth portions.
