An image forming apparatus includes a plurality of toner-image forming units. Each toner-image forming unit includes a photosensitive drum and a charging unit that is arranged to abut against or remain detached from the photosensitive drum, and that electrically charges the photosensitive drum. Each of the toner-image forming units forms an image of a different color. At least one of the charging units functions as a corona charging unit and at least another one of the charging units functions as a non-contact charging unit.