To provide an improved ventilation device by solving disadvantages of a conventional embodiment.

A vent valve device 1 has a packing element 4 which is provided in a hole 3 on a plate side and stored in the hole in a sealed condition, a disk-shaped closing plate 6 which is operated against the restoration force for the opening/closing operation, and cooperated with the packing element, and a vent valve support plate 2 having filtering screens 10 and 12 with the packing element stretched on the side facing the closing plate. The vent valve device 1 is provided on a bulkhead 13 to separate two chambers 14 and 15, and opens/closes a passage for medium passing through the bulkhead 13. To generate the restoration force, a spring element 7 which is disposed on the closing plate, grasps the packing element 4, and resists the opposing side is provided on the vent valve device 1.