To easily mount a plurality of plate materials forming angles of 45-135° at which mounting is difficult usually.

A nut 14 is thread-engaged from an upper end of a feed screw 13 of a soft suction cup 11 sucked to the plate material R, and a hard suction cup 12 and a suction-side arm 21 of a connection arm 20 are clamped and fixed between the nut 14 and the soft suction cup 11. Furthermore, when the nut 14 is rotated, the soft suction cup 11 is pulled up, atmospheric pressure in the soft suction cup 11 is reduced, and a suction force of the soft suction cup 11 is increased. However, a peripheral edge of the soft suction cup 11 is pressed by a peripheral edge 12c of the hard suction cup 12 and fixed, and the suction side arm 21 and the entire part of the connection arm 20 are also fixed to the plate material R. When a press screw (press body) 30 of the pressing-side arm 22 of the connection arm 20 is turned, an end edge of the plate material S is pressed and fixed to an end edge of the plate material R, and an end of the plate material S is connected and fixed to the end of the plate material R.