An operative instrument includes forceps (2) having a treating section (2a) for treating an anatomy at an extremity and being provided with a heat-generating body (23) for generating heat to be provided to the anatomy and a power supply unit (3) for supplying electric power to the heat-generating body of the forceps. The operative instrument raises the temperature of the heat-generating body by supplying substantially constant electric power to the heat-generating body. Therefore, coagulation and incision of the anatomy can be performed satisfactorily.
