In an image reading apparatus which can read a transparent original and reflection original, a white background is formed like a sheet. The image reading apparatus is arranged to be movable by a pair of rollers which rotate using, e.g., the driving source of an original feeder. To read a transparent original, the white sheet is moved by the pair of rollers to a position where a transparent original reading illumination unit is exposed. This makes it possible to eliminate trouble in detaching the white background mounted on the back of an original platen in accordance with the type of an original to be read.