To integrate a high-safety fixed function against illegal cancel without making production expensive in spite of complicated structure by fitting a fixed element to a connection element to strongly fix merchandise, fixing it and canceling the connection element through the flowing operation of gas.

When a connection element 4 to be inserted into merchandise is inserted into a fixed element 6, a fixing means 34 strongly presses the connection element 4 so that the connection element 4 can be fixed. When the connection element 4 is tried to be pulled out, the connection element 4 is strongly fixed. When a releasing means 8 is operated for releasing the merchandise, air or any other suitable gas is led into an internal passage 56. Then, the fixing means 34 is finally moved to the side and the pressure applied to the connection element 4 is stopped. Therefore, merchandise 10 can be released from the fixed element 6.