PURPOSE: To execute sealing with good energy efficiency by actuating a web up door having a perpendicular discharge seal of multiple planes for a drying machine of a graphic art in a perpendicular direction by a pneumatic system.

CONSTITUTION: When a box-shaped member 76 of the web up door 10 is moved upward within a door approach opening duct 78 by extension of a pneumatic cylinder, an upper surface 76d, sealing action flange members 30a, 30c or the like come into pressurized contact with opposite gasket members 32d, 32c or the like, thereby completely sealing the opening duct 78, i.e., the interior of the drying machine from the external ambient air. In such a case, the sealing pressure is regulated by threaded stopper rods 130a to 130n and adjusting screws 150a to 150n. The perpendicular discharge seal 11 moves upward together with the box-shaped member 76 and is aligned as a protective barrier. The safe sealing of the good energy efficiency is thus executed.