a housing to which a cylindrical image bearing body is rotatably attached;

a charging roller configured to come into contact with a surface of the image bearing body and charge the surface to a predetermined potential;

an image forming section configured to form an image on a charged surface of the image bearing body;

a bearing member rotatably supporting a rotating shaft of the charging roller;

a holding member configured to hold the bearing member in a state in which the charging roller is movable in a first direction orthogonal to the rotating shaft;

an urging member configured to urge the bearing member in the first direction with respect to the holding member;

a fixing section configured to fix the bearing member in a first position on an upstream side in the first direction with respect to the holding member; and

an unfixing section configured to, in a state in which the bearing member is fixed in the first position with respect to the holding member by the fixing section, separate the charging roller from the surface of the image bearing body so as to be opposed to the surface and position the holding member in the housing and, thereafter, unfix the bearing member fixed by the fixing section with an operation for sliding the holding member in a second direction parallel to the rotating shaft, move the bearing member to a second position on a downstream side in the first direction with an urging force of the urging member, and bring the charging roller into contact with the surface of the image bearing body.