An exposure device comprising a table having a plane on which an original is placed, a light emitting device for emitting a light on the original placed on the plane, a scanning device for scanning the original on the plane while the emitting device is being moved along the plane, and a light adjusting device for adjusting the quantity of light emitted from the emitting device. The light adjusting device includes a shutter adapted to narrow the path of light emitted from the emitting device and adjust the quantity of light, an urging member for urging the shutter in a predetermined direction, an operating member for operating the shutter against the urging force of the urging member, when the emitting device is being moved and the shutter abuts against the operating member, and a holding device for holding the shutter, which has been moved to a predetermined position by the operating member, until the shutter abuts against the operating member again.