In an image forming apparatus, a toner cartridge is removably set to a toner supply device and used while being set to the toner supply device, and the toner cartridge includes a main body with a toner supply port and a spiral agitator being disposed within the main body and rotated by drive means.The apparatus also includes a reserve tank for a toner dispensing section including a toner container for containing toner supplied from a cartridge, and a toner supply section for receiving toner from the toner container and supplying the received toner to a developing unit. The toner container includes a spiral agitator for supplying toner to the toner supply section. An auger for transferring toner to the developing unit is disposed in the toner supply section. A toner transfer power of the spiral agitator is larger than that of the auger.An empty detector is disposed at such a location that, unsoiled by toner leaked from the toner cartridge, the empty sensor can sense, within the reserve tank, such an amount of toner left in the reserve tank as to allow the toner to be dispensed a prescribed number of times. A display means is also provided for displaying an empty state of the reserve tank according to an empty signal derived from the empty sensor.