A developer cartridge that can be attached to and detached from an image forming apparatus and contains developer, the developer cartridge includes: a first body that has an opening for supplying the developer; a second body that covers the first body, the second body having a conductive portion that can transmit electricity; and a memory unit that is disposed between the first body and the second body, the memory unit can be connected to a terminal of the image forming apparatus through the conductive portion of the second body, wherein the second body and the first body are movable relative to each other, the second body is able to open and close the opening by a relative movement with regard to the first body.