The present invention provides an image forming apparatus (210) as well as a developing cartridge (240) for use in an image forming apparatus, wherein a contact plate of an electrode (247) of the developing catridge is disposed to contact a bias terminal (258) coupled to a first wall (251a) of a drum unit (250) when the developing cartridge is installed in a developing cartridge installation portion (250a), and wherein a position where the electrode contacts the bias terminal when the developing cartridge is installed in a developing cartridge installation portion is inside an outer shape of the driven coupling (248a1) when viewed in a direction of the developing roller shaft (244a).