PURPOSE: To hold parts to be treated with pressure members and to release and travel the parts to be treated after treatment by holding the pressure members to each end parts of two arms and connecting the pressure members to a drive means mutually moving the arms.

CONSTITUTION: When a motor is rotated in the given direction, a nut 32 which is blocked in moving, pushes back a rod outward to close a holding tool. When an electrode 24 is brought in contact with a metal sheet 13, a rotor 31 continues the rotation up to an upper electrode 23, at the moment when the rotor 31 is brought in contact with a metal sheet 12, the motor gives fixed torque, the metal sheets to be generated between two electrodes can be held. The motor is rotated in the other direction to open so that the nut 32 moves the rod 11 to the inside of the motor and an upper arm 3 is pulled back to an open position through a york 39 of a shaft 40. At the same time, when a connecting part 44 is engage with, the motor moving forward owing to a port 38 is rotated in the direction to open the rotation of a lower arm 2.