A scanning device comprises a light source, a reflecting mirror and a photosensor. The light source provides light to an original. A first portion of the light penetrates through a hole of the original and becomes penetrating light. A second portion of the light is reflected by a hole-free portion of the original and becomes second reflected light. The reflecting mirror reflects the penetrating light and generates first reflected light. The photosensor receives the first reflected light and the second reflected light and generates a hole-containing image signal representative of an image of the original.