The photosensitive conductor unit includes a casing, and a protective cover, wherein: the casing includes an engaging portion on an insertion-side end and a guide portion slidably guiding the protective cover in proximity to an opposite end to the insertion-side end of the photosensitive conductor unit; the protective cover includes a hook portion engaging with the engaging portion, a positioning portion determining the position of the protective cover, a side wall covering an exposed portion of the surface by extending along an axial direction of the photosensitive conductor drum, and a rail portion extending in the insertion direction of the photosensitive conductor unit in proximity to both ends of the side wall in a direction orthogonal to the axial direction of the photosensitive conductor drum and engaging with the guide portion such that the guide portion slidably guides the protective cover.