An image forming apparatus includes: a document reading unit 110 allowing input of image data generated from a read document, a paper feed unit 140 containing recording paper, an image forming unit 120 forming an image on the recording paper based on the image data, and a touch-panel display 132 displaying a preview image representing a state of image formation. The touch-panel display displays a preview image in a designated orientation for a document of a prescribed size, and displays a preview image in accordance with size and orientation of recording paper fed from the paper feed unit, for a document not of the prescribed size. Thus, for documents of a prescribed size, preview images in a prescribed orientation can be displayed regardless of the direction of arrangement of the recording paper, and easier confirmation of expected finish of the formed image becomes possible.