An improved developer for an electrophotographic image forming apparatus is provided. The developer includes a developer frame, a plurality of developing cartridges that are sequentially mounted in the developer frame and have a plurality of toner feeding units for receiving respective toners. A plurality of toner cartridges feed the respective toners to the plurality of toner feeding units, respectively. A toner cartridge frame is detachably mounted in the developer frame and in which the plurality of toner cartridges are mounted.