There is provided an image forming apparatus including a main body, a drum cartridge attachable to and detachable from the main body and including a photosensitive drum, a developing agent cartridge attachable to and detachable from the main body and containing a developing agent to be supplied to the photosensitive drum, and an exposure unit configured to expose a surface of the photosensitive drum. The main body includes a drum cartridge guide which is configured to guide the drum cartridge such that the drum cartridge passes above the exposure unit, when the drum cartridge is attached to or detached from the main body, and a developing cartridge guide which is configured to guide the developing agent cartridge such that the developing agent cartridge passes below the exposure unit, when the developing agent cartridge is attached to or detached from the main body.