Abstract: An image forming device includes a main casing, a photosensitive drum unit and a developing device unit. The photosensitive drum unit includes a plurality of photosensitive drums juxtaposed in a first direction orthogonal to an axis of each photosensitive drum. The developing device unit includes a plurality of developing devices disposed in one-to-one correspondence with the plurality of photosensitive drums and a supporting member. Each developing device includes a developing roller having a shaft extending in a second direction parallel to the axis of each photosensitive drum. The supporting member supports the developing devices to be movable between a first position for supplying toner to corresponding photosensitive drums and a second position retracted from the first position. The developing device unit is detachable from the main casing by moving the developing devices to the second position and drawing the supporting member.