A toner cartridge assembly corresponding to a photosensitive drum cartridge disposed at a printing apparatus body. The toner cartridge assembly develops toner on the photosensitive drum and collects used toner and includes a toner cartridge corresponding to the photosensitive drum cartridge at the body, the toner cartridge having a developing roller to develop the stored toner on the photosensitive drum; and a used toner chamber movably connected with one side of the toner cartridge to store used toner collected from the photosensitive drum cartridge. The used toner chamber is fixed at a predetermined position on the printing apparatus body, and the toner cartridge adjusts a developing nip between the photosensitive drum and the developing roller by being connected with the used toner chamber in a way that the toner cartridge can reciprocate and rotate in a direction of the photosensitive drum.