A charging device includes a corona charger; a shutter of a sheet for shielding an opening of said corona charger, the sheet having such a property that it is curled about an axis when said shutter absorbs moisture; and a winding-up device for winding up the shutter. The axis and a winding-up direction in which the shutter is wound up by the winding-up means form an angle therebetween from 45 degrees to 135 degrees.