Abstract: An electric surgical operation apparatus comprises: an active electrode which performs medical treatment to an area to be treated by applying electric energy to the area; an electric power supplying unit which supplies electric power to the active electrode; a measuring unit which measures at least one of the electrical power output voltage value supplied to the active electrode from the electric power supplying unit, and the output current value thereof; a discerning unit for discerning whether or not the change in at least one of the voltage value and the current value measured by the measuring unit has attained a predetermined change amount; and a voltage control unit for controlling the electric power supplying unit so that the supplied electric power is a constant voltage, according to the discerning results discerned by the discerning unit.