On a touch-panel display of an image forming apparatus, a function selecting area and a preview area are displayed next to each other. On the function selecting area, a function setting menu is displayed in one display mode among an icon mode in which only a group of icons are displayed, a regular mode in which a group of icons and a group of texts are displayed, and an express mode in which a group of icons, a group of texts and a group of function setting buttons are displayed. In the icon mode, detailed preview information is displayed on a large preview area, and in the express mode, detailed function selecting information is displayed on a large function selecting area.