To provide a cover device, which is brought to an open state not integrated to a building area in the normal case, in which an opening section is closed when wind pressure higher than a fixed quantity works and which can prevent an infiltration to the inside of wind and rain.

The cover device is composed of a frame-shaped frame, a large number of open-close blades, in which both ends are supported pivotally to one opposed frame member of the frame at prescribed intervals, which are rotated by wind pressure when wind pressure higher than the fixed quantity works and which close the opening section of the frame, and open-close blade supporting means being installed to the open-close blades, maintain the open state in the normal case and work so as to close the opening section of the frame by wind pressure when wind pressure higher than the fixed quantity works.