to feed air onto the surfaces the display surface of the liquid crystal panel of the pair of substrates 1 for pressurization the o rings 4 are formed also on the interposed jigs 5 and the upper jig 10 to be described later the air inlet holes 6 are formed also in the interposed jigs 5 and the upper jig 10 to be described later through the corresponding connection pipes 7 the air inlet holes 6 feed compressed air from a supply source 15 onto the surfaces of the corresponding pairs of substrates 1 through the air inlet pipe 8 the interposed jig 5 is arranged above each pair of substrates 1 the interposed jig 5 has the o rings 4 identical to that of the lower jig 11 on its upper and lower surfaces the o ring 4 is arranged to correspond to the outermost thermosetting resin 2 within the pair of substrates 1 furthermore pairs of substrates 1 and the interposed jigs 5 are alternately stacked and the upper jig 10 is arranged on the uppermost pair of substrates 1 the upper jig 10 has an o ring 4 on its lower surface this o ring 4 is arranged to correspond to the outermost thermosetting resin 2 within the pair of substrates 1 the press plate 12 is arranged on the upper jig 10 the press plate 12 presses members ranging from the upper jig 10 to the lower jig 11 with a predetermined pressure the oven 9 has the hot air inlet holes 14.