A image forming device includes a main casing, a photosensitive-member unit including a plurality of photosensitive members aligned in a first direction, and a belt disposed in confrontation with the photosensitive members. The photosensitive-member unit is movable in the first direction with respect to the main casing, and is pulled out of the main casing when pulled in a pull-out direction parallel to the first direction. The photosensitive-member unit is provided with a cleaning member that is disposed on an upstream side of a most-upstream one of the photosensitive members with respect to the pull-out direction. The cleaning member slidingly contacts the belt when the photosensitive-member unit is moved with respect to the main casing. The cleaning member is located at a predetermined position separate from the belt when the photosensitive-member unit is at a mounting position within the main casing.