A disk array device includes hard disks from which RAID groups are configured. This image forming apparatus is arranged to print document images in a preset number on a half of a single paper sheet when the writing space mode has been set as a copying mode. The skirt has an annular score line and an annular fold line extending therearound. The inclined interface is permeated along the path with projected light form the light-emitting part when remaining content is present and reflects projected light from the light-emitting part out of the path when remaining content is absent.