An image forming apparatus, that is controlled to perform image output based on electrophotography, includes: an image processor for outputting input image information in the form of image data for forming images; and, an image forming portion for forming images on a sheet of paper based on the image data output from the image processor. The image processor has a function which, in accordance with folding information for folding the paper with images formed thereon, sets the images to be formed on the page of the folded paper whose folded sections oppose each other when the paper has been folded.