A developing device to prevent damage of a memory unit and poor connection between terminals of the memory unit and a main body of an image forming apparatus, by improving a mounting position of the memory unit. The developing device is removably mounted to a main body of the image forming apparatus. The memory unit includes terminals exposed through a rear side of the developing device. The memory unit is disposed closer to a power reception unit formed at one side of the developing device than to a driving force reception unit formed at an other side of the developing device.