PURPOSE: To enable the release of connection even if stopping the supply of a fluid for driving a cylinder in a device body.

CONSTITUTION: Compressed air is supplied from a port 5 to push a piston part 3 downward, and a claw 6 is opened being moved in the axial and right-angled directions by the piston 5. The pins 8 of a device body 1 and the holes of a connecting part 9 are adjusted and connected, and the compressed air is exhausted from the port 5. The piston part 3 is thereby moved upward by a compression spring 4, and the claw 6 is closed by a tension spring 7 to perform connection. Even without the supply of compressed air, the claw 6 is opened by pressing a shaft 10, and the connecting part 9 can be released.