An image forming apparatus includes at least one process cartridge removably mounted on an apparatus body and including at least an image carrier on which a toner image is to be formed and a cleaning device configured to remove toner left after image transfer with a cleaning blade. A hole for passing a light beam emitted from an optical writing unit toward the image carrier therethrough is formed in part of a case bottom wall of the process cartridge higher in level than part of the case bottom wall below the cleaning blade.