A display device for a copying machine, wherein when a special mode such as copying with reduction and duplex copying (copying on both surfaces of a copying paper) is selected, it is judged whether the paper feed cassette set for copying is proper for the mode selected and if so, the paper feed cassette set for copying is displayed, while if not, the applicable paper feed cassettes are displayed successively, and furthermore, the paper size stacked in the paper feed cassette is displayed regardless of whether it is in the metric size system or the inch size system.