[Object] To stably open and close an electrode. [Solving Means] A protrusion portion 33f is provided in a shaft portion 33a of an insulation spacer 33 rotatably supporting a pair of forceps pieces 31a and 31b. An inner peripheral surface of a shaft hole 31c of the forceps piece is provided with a notch portion 31h. The notch portion 31h includes an end portion 31i with which a protrusion portion comes into contact when grip portions of the forceps pieces rotate in an approaching (closing) direction and an end portion 31j with which a protrusion portion comes into contact when the grip portions of the forceps pieces rotate in a separating (opening) direction.
