Provided is a waste developer container to be fixed to an image forming device including a developing device and a waste developer amount detection unit for obtaining information on an amount of accumulated waste developer discharged from the developing device, wherein the developing device uses toner image carrier holding a toner image and two-component developer to form a toner image, the waste developer amount detection unit obtains the information on the accumulated amount by emission and reception of light, and the waste developer container includes: a container space for containing waste developer discharged; a detection window for passing light that is emitted from the waste developer amount detection unit, passes the container space, and is incident again to the waste developer amount detection unit; and a magnet provided to a position where a magnetic force is applied to the detection window and light passing the detection window is not shut.