An image forming apparatus includes a photosensitive member and a developing device. The developing device includes a developing roller to supply a developer to the photosensitive member and a casing defining an external appearance of the developing device. A first auger section is defined in the casing to agitate and convey the developer, and a second auger section is defined in the casing and divided from the first auger section. A developer delivery unit is provided on the outside of the casing to deliver the developer from the first auger section to the second auger section.