an image forming apparatus that includes : an image carrier ; a developing cartridge detachably mountable with respect to the image carrier ; a processing device to which voltage acting between the image carrier and the processing device is applied ; and a first electrode , wherein the developing cartridge further includes : a developing roller on which toner is capable of being held ; and a second electrode capable of being electrically connected with the first electrode when the developing cartridge is mounted with respect to the image carrier , the processing device further includes : a third electrode capable of being electrically connected with the second electrode when the developing cartridge is mounted with respect to the image carrier , wherein the second electrode positions the developing cartridge in an axial direction of the developing roller .