An image forming device comprising: a main unit including a main unit electrode; and a tandem type of process unit removably loaded in the main unit, the tandem type of process unit comprising: a plurality of process cartridges, each of the plurality of process cartridges having a photosensitive drum rotatable about an axis extending in a first direction, each of the plurality of process cartridges having two side faces facing each other in the first direction and a cartridge electrode provided on one of the side faces, the plurality of process cartridges being aligned in a second direction perpendicular to the first direction; characterized by a pair of lower supporting plates, each of the lower supporting plates supporting a lower part of each side face of each of the plurality of process cartridges; and a pair of upper supporting plates positioned upward and separately from the pair of lower supporting plates, each of the upper supporting plates supporting an upper part of each side face of each of the plurality of process cartridges, and a pair of joint plates facing each other in the second direction and coupling the pair of lower supporting plates to the pair of upper supporting plates wherein the pair of upper support plates and the pair of lower support plates provide a side opening facing each side face of each of the plurality of process cartridges to expose the cartridge electrode of each of the plurality of process cartridges toward outside through the side opening and wherein the cartridge electrode is adapted to directly connect to the main unit electrode, a connected portion of the cartridge electrode and the main unit electrode is inside of the inner surface of the upper support plate in the first direction. a main unit including a main unit electrode; and a tandem type of process unit removably loaded in the main unit, the tandem type of process unit comprising: a plurality of process cartridges, each of the plurality of process cartridges having a photosensitive drum rotatable about an axis extending in a first direction, each of the plurality of process cartridges having two side faces facing each other in the first direction and a cartridge electrode provided on one of the side faces, the plurality of process cartridges being aligned in a second direction perpendicular to the first direction; a plurality of process cartridges, each of the plurality of process cartridges having a photosensitive drum rotatable about an axis extending in a first direction, each of the plurality of process cartridges having two side faces facing each other in the first direction and a cartridge electrode provided on one of the side faces, the plurality of process cartridges being aligned in a second direction perpendicular to the first direction; a pair of lower supporting plates, each of the lower supporting plates supporting a lower part of each side face of each of the plurality of process cartridges; a pair of upper supporting plates positioned upward and separately from the pair of lower supporting plates, each of the upper supporting plates supporting an upper part of each side face of each of the plurality of process cartridges, and a pair of joint plates facing each other in the second direction and coupling the pair of lower supporting plates to the pair of upper supporting plates the pair of upper support plates and the pair of lower support plates provide a side opening facing each side face of each of the plurality of process cartridges to expose the cartridge electrode of each of the plurality of process cartridges toward outside through the side opening and wherein the cartridge electrode is adapted to directly connect to the main unit electrode, a connected portion of the cartridge electrode and the main unit electrode is inside of the inner surface of the upper support plate in the first direction.