Patent ID: 8311459

Claim:
A developing apparatus comprising: a housing which contains toner in the interior thereof; a toner supporting roller which is mounted by shafts in the housing and rotates while supporting electrification toner which is supplied from the housing to the surface thereof; and an electrically-conductive regulating blade which comes into contact with the surface of the toner supporting roller, thereby regulating the amount of toner which is supported on the surface of the toner supporting roller, wherein regulating bias voltage having the same polarity as the electrification polarity of the toner is applied to the regulating blade, the toner includes, as external additives, an insulating external additive and an electrically-conductive external additive that is higher in conductive property than the insulating external additive, and in addition, satisfies any of the following first to third conditions, the first condition: a volume average grain diameter of the electrically-conductive external additive is larger than a volume average grain diameter of the insulating external additive, the second condition: a volume average grain diameter of the electrically-conductive external additive is larger than a volume average grain diameter of the insulating external additive in which coverage in the toner is higher than that of the electrically-conductive external additive, and the third condition: coverage of the electrically-conductive external additive in the toner is higher than coverage of the insulating external additive that is larger in volume average grain diameter than the electrically-conductive external additive.