Image forming apparatus

An image forming apparatus, comprising:

• an image bearing member on which an electrostatic latent image is formed;
• a developing device which is disposed opposite to the image bearing member, includes a toner bearing member which bears toner on its surface and conveys the toner, develops the electrostatic latent image formed on the image bearing member with the toner that has been conveyed by the toner bearing member, and forms a toner image on the image bearing member;
• a transfer device which transfers the toner image formed by the developing device, to a recording medium;
• and
• a cleaning device which removes the toner remaining on the image bearing member after the transfer,
• wherein a surface of the toner bearing member is subjected to alumite treatment,
• the toner 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, and
• 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.