The image forming apparatus is an image forming apparatus including an image bearing member, a developing device, a transfer device, and a cleaning device. The developing device includes a toner bearing member having a surface subjected to alumite treatment. Toner that is used in the image forming apparatus is magnetic mono-component developer including magnetic toner particles containing at least binder resin and iron-containing magnetic powder, and an external additive to be externally added to the magnetic toner particles. The external additive is formed from inorganic fine particles which have been subjected to surface treatment with a tin-containing compound and an antimony-containing compound. In the image forming apparatus, the ratio of antimony to iron of the toner that has been removed by the cleaning device is double or more the ratio of antimony to iron of the toner before being conveyed by the toner bearing member.