A toner cartridge includes a toner accommodating unit including first and second accommodating portions and includes a light transmitting portion having an incident surface and an emergent surface. The toner accommodating unit includes first and second end portions with respect to a first direction and includes third and fourth end portions with respect to a second direction crossing the first direction. The first accommodating portion is provided with a discharge opening, and the second accommodating portion is provided with a receiving opening. The discharge opening and the receiving opening are positioned closer to the third end potion than to the fourth end portion in the second direction. The incident surface and the emergent surface are provided in positions closer to the fourth end portion than to the third end portion in the second direction and are exposed to an outside of the cartridge.