An image forming device is provided, which includes an interlocking mechanism that causes a cleaning unit to clean with a cleaning surface thereof a detection surface of a detection sensor for reading each detection pattern formed on an outer surface of a sheet-feeding endless belt, in conjunction with movement of a drawer, which holds a plurality of process cartridges, between an attachment position where a photoconductive drum included in each process cartridge faces an up-facing side of the outer surface of the endless belt and a replacement position where at least one of the process cartridges is outside a main body housing of the image forming device.