An image forming apparatus includes a reading unit configured to read an original, an image forming unit configured to form an image of the original read by the reading unit on a sheet, a detecting unit configured to detect whether or not the image of the original read by the reading unit includes an irregular part formed by a stray dust particle adhered to the original, and a control unit configured to control, in response to detection of the irregular part by the detecting unit, the image forming unit to make an additional copy of the image of the original including the irregular part.