An image forming apparatus, including a casing, a toner cartridge, and a process cartridge, is provided. The toner cartridge detachably attached to the casing stores toner therein. The process cartridge detachably attached to the casing includes a developing unit and a drum unit. The developing unit includes a developer roller and a toner conveyer tube. The toner conveyer tube has a first opening, through which the toner from the toner cartridge is acceptable into the toner conveyer tube while the toner cartridge and the process cartridge are attached to the casing. The drum unit includes a photosensitive drum supporting the toner conveyer tube by contacting a circumferential surface of the toner conveyer tube. The developing unit is pivotable with respect to the drum unit with the toner conveyer tube and the drum unit being slidable on each other.