PURPOSE: To easily open a door loaded with pressure.

CONSTITUTION: A support arm 1, a pedal 2, and a pressure arm 3 are pivotted in a hole in the width direction of respective edges by a pivotal shaft 4. The pressure arm 3 is made longer than the longitudinal length of the pedal plate 2. At the one end thereof, a roller 3a is provided and further, connected by the pedal pate 2 and a joint member 5. And a magnet is fitted to the back face of the pedal plate 2 as a temporary stopper. The push-and open mechanism of the pressure door is a high-pressure chamber preventing smoke from entering due to the pressure to open the door arranged in the space from the adjacent room. The pressure arm 3 is arranged in front of the door and the lower end of the support arm 1 is pivoted at the lower part of the wall adjacent to the door and the pedal plate 2 is temporarily fitted on the wall by the magnet 6. When the door is closed, the pedal plate 2 is lowered due to the removed magnet resulting from the impulse. When the pedal plate 2 is trod, the pressure arm 3 is tumbled to force the roller 3a to slide on the door and to open the door.