Patent ID: 7742725

Claim:
A developing device comprising: a developer carrier that carries developer; a developing case that supports the developer carrier; and a toner cartridge that houses the developer and is attachable to and detachable from the developing case, wherein the toner cartridge comprises: a toner case comprising a first opening for supplying the developer to the developing case; and a first blocking member that opens and closes the first opening, wherein the developing case comprises: a second opening for receiving the developer supplied from the first opening; a second blocking member that opens and closes the second opening; and an opening/closing member that is swingably disposed on the developing case and opens and closes the first blocking member and the second blocking member, wherein the opening/closing member is swingable among predetermined positions, the predetermined positions comprising: a first position where the toner cartridge is detached from the developing case and the second opening is closed; a second position where the toner cartridge is attached to the developing case and the first opening and the second opening are opened to communicate with each other; and a third position where the toner cartridge is attached to the developing case and the first opening and the second opening are closed to block communication between the first opening and the second opening, the third position being between the first position and the second position, and wherein the opening/closing member swings from the first position to the third position in accordance with attachment of the toner cartridge to the developing case.