An image forming apparatus includes a first read device configured to read a first surface of an original document in a main scanning direction and to produce a first band data. The image forming apparatus further includes a second read device configured to read a second surface of the original document in the main scanning direction and to produce a second band data during the reading of the first surface by the first read device. The image forming apparatus still further includes an image data processor configured to produce printing band data by combining the first band data with the second band data, during the reading of at least one of the first surface and the second surface. Moreover, the image forming apparatus includes a printing device configured to start printing an image of the printing band data produced by the image data processor on a printing sheet, during the reading of at least one of the first surface and the second surface.