An image-forming device includes a plurality of photosensitive drums, a plurality of drum gears, a plurality of drive gears and a removal allowing unit. Each drum gear has a first target portion. Each drive gear has a second target portion. The removal allowing unit allows each photosensitive drum to be removed from the casing only when the first target portion of the drum gear is positionally in coincidence with a first position and when the second target portion of the drive gear is positionally in coincidence with a second position.