<；P>；PROBLEM TO BE SOLVED: To reduce the cost of a ventilation device by avoiding making it larger. <；P>；SOLUTION: The ventilation device includes a frame 1 that forms an opening on a greenhouse H, a cover 2 with one side pivotally supported on the frame 1 or on a neighboring position thereof to open/close the opening, and a drive mechanism 3 that causes the cover 2 to swing relative to the frame 1. The drive mechanism 3 includes a support 4 held on the frame 1 or on a neighboring position thereof, a drive arm member 5 that links its tip arm member 5b to the cover 2 with its base-end worm wheel member 5a pivotally supported on the support 4, and a drive shaft 6 held by the support 4 with its tip screw member 6a engaged with the base-end worm wheel member 5a of the drive arm member 5. The drive shaft 6 is rotated by an external force inputted to its base-end input member 6b protruding out of the support 4 to rotate the base-end worm wheel member 5a of the drive arm member 5. By the rotation of the base-end worm wheel member 5a, the drive arm member 5 swings the tip arm member 5b, whereby the cover 2 is moved to open/close the opening. <；P>；COPYRIGHT: (C)2011,JPO&INPIT
