Shutter mechanism of light irradiation apparatus

The present invention provides a shutter mechanism which occupies a smaller area with a shutter plate, does not require a large size shutter drive mechanism, and can effectively cool the shutter plate. The light beam emitted from a light irradiating source is shielded by a shutter plate 11a. The shutter can be opened by moving the shutter plate 11a upward with an air-cylinder 16a. In this case, a cooling nozzle 14a also moves together with the shutter plate 11a, and the center area of the shutter plate 11a is always cooled by the cooling air. The shutter can also be closed by moving a shutter plate 11b upward with an air cylinder 16b. Thereby, the light beam is shielded by the shutter plate 11b. A cooling nozzle 14b moves together with the shutter plate 11b, and the shutter plate 11b is cooled by the cooling air at all times. Next, the shutter can then be opened by moving the shutter plate 11b downward, and the shutter is closed by moving the shutter plate 11a downward.