An image forming apparatus includes: a hardware processor that: generates image data for composition; and divides the image data for composition into bands; an output memory; a storage that determines whether image data of each band coincides with image data of another band, secures a unique region, transfers the image data of the band to the unique region and associates the band with the unique region, secures common regions, transfers the image data of one of the bands to the common region and associates any one of the common regions to each of the bands; a reader that reads the image data from the region associated with each band and outputs the image data for composition; a composer that composes the image data for composition with the image data to be printed; and an image former that forms an image based on the composed image data.