A shutter device reduces resistance in an air passage while maintaining air-tightness, thus reducing a load to a fan and a motor. A shutter mount is provided between an intake port adapted to be connected with a side from which air enters and a discharging port adapted to be connected with a side from which air is discharged. A shutter frame is inserted into an inside of the shutter mount. A shutter for preventing outside air from entering from the discharging port is mounted to the shutter frame. The shutter mount has a rib thereof for sealing a gap produced between the shutter and the shutter mount when the shutter is closed. The rib has an inner diameter substantially equal to a diameter of the discharging port as seen from the discharging port.