Abstract: A toner cartridge extends in a longitudinal direction, and is detachably attached to an image drum unit. A memory element is electrically connected to an electrical terminal. The toner cartridge includes a first end portion on which the electrical terminal is disposed and a second end portion longitudinally opposite to the first end portion. An engagement portion is formed on the outer surface of the toner cartridge in the vicinity of the first end portion. When the toner cartridge is attached into the image drum unit, the second end portion engages the image drum unit, and the engagement portion engages the image drum unit such that the toner cartridge is urged against the image drum unit.