A toner cartridge with a cartridge body having a toner supply opening, a seal member, having a folded part, for closing the toner supply opening with a portion between the folded part and an end, and a rolling mechanism for rolling up the seal member from the end which is free of the closing of the toner supply opening. Both side ends of the seal member near the rolling mechanism are different in length between the folded part and the rolling mechanism. Another toner cartridge has a plurality of seal members which have different length. The toner cartridges may have a pressing member for pressing the outer surface of the seal member rolled up by the rolling mechanism. These toner cartridges can be applied to a developing unit in a copying machine.