<p>A shutter device comprises the following: a rib provided on the inner wall of a ventilation duct part; and a shutter plate that abuts the rib and is axially supported by the inner wall of the ventilation duct part by holding parts that are provided at left and right ends. The holding parts are provided above the center line of the ventilation duct part. A U-shaped projecting part, which opens downward with respect to the rotating shaft that connects shaft support parts of the shutter plate, is provided on the shutter plate so as to project towards the ventilation downstream side of the shutter plate.</p>
