An image forming apparatus including a cartridge that has a photosensitive drum and can be attached to and detached from a main body of the image forming apparatus, an optical device that has a cover glass through which light emitted toward the photosensitive drum passes, a cleaning member that can move from a cleaning start position to a cleaning end position for cleaning the cover glass, and a lock member that prevents the cleaning member from moving. Before the cartridge is attached, the lock member prevents the cleaning member from moving in the longitudinal direction of the cover glass. During the attachment of the cartridge, the cartridge engages with the lock member and unlocks the cleaning member and enables the cleaning member to move from the cleaning start position.