An image forming apparatus includes a toner cartridge which is detachably mounted from a first direction to store a toner; and a processing unit which is detachably mounted from a second direction perpendicular to the first direction and is provided with a photoconductor, a developing section for supplying a toner fed from the toner cartridge to the surface of the photoconductor to convert an electrostatic latent image to a toner image and a cleaning section for collecting the toner adhered on the surface of the photoconductor.