An image-forming device includes: a main casing; a retaining member; developing units retained by the retaining member; toner cartridges; and an operating member provided at the retaining member. The retaining member is movably disposed between a position inside an accommodation space in the main casing, and a pull-out position. The toner cartridges are detachably attachable to the retaining member, when the retaining member is at the pull-out position. Each toner cartridge includes: a casing in which a through-hole is formed for supplying toner to a corresponding developing unit; and a shutter that moves between open and closed positions exposing and closing the through-hole, respectively. The operating member moves the shutter between the open and closed positions by shifting between first and second positions in which the operating member extends above the retaining member, and in which the operating member has a lower profile than in the first position, respectively.