In an image forming apparatus, a process frame is movable into and out of a main casing in a first direction. The process frame includes a first wall and a second wall spaced apart from the first wall in a second direction. A first cartridge is detachably mountable to the process frame in a third direction crossing the second direction. A first electrode protrudes from an outer surface of the first cartridge outwardly in the second direction. In a state where the first cartridge is mounted to the process frame, the first cartridge is positioned between the first wall and second wall of the process frame in the second direction and a portion of the first wall aligns with the first electrode in the third direction such that the portion of the first wall is overlapped with the first electrode as viewed in the third direction.