A photosensitive member unit includes: a first image forming unit including a first photosensitive member rotatable on a first axis line; and a second image forming unit including a second photosensitive member rotatable on a second axis line parallel with the first axis line and disposed in parallel with the first image forming unit at a first side in an orthogonal direction perpendicular to the first and second axis lines. The first image forming unit includes a charger and a cartridge containing portion. The charger includes: a charging member; a cleaning member for cleaning the charging member; and an operating member for operating the cleaning member. The operating member is inoperable when the developing cartridge is installed in the cartridge containing portion, and is exposed to be operable in the cartridge containing portion when the developing cartridge is removed from the cartridge containing portion.