Patent ID: 7693433

Claim:
An image forming apparatus comprising: an image carrier that rotates and carries a toner image by a surface layer disposed on a surface thereof; a charging roll that charges the surface layer of the image carrier while the image carrier completes one or more rotations; a power supply unit that supplies a current to the charging roll; a detector that detects the current that the power supply unit outputs; a leak current detector that detects a leak current included in the current that the detector has detected; a layer thickness calculating unit that calculates a numerical value relating to the thickness of the surface layer of the image carrier on the basis of the current that the detector has detected; and a current leak state determining unit that determines a current leak state on the basis of the current that the detector has detected and the leak current that the leak current detector has detected, wherein the layer thickness calculating unit determines whether or not it should calculate the numerical value relating to the thickness of the surface layer in accordance with the determination result of the current leak state determining unit.