An image forming apparatus is described. The image forming apparatus may include a developer cartridge and a photosensitive unit. The developer cartridge may include a first casing accommodating a developing agent, a developing agent carrier supported by the first casing and carrying the developing agent, a memory element storing predetermined information, and a first terminal electrically connected with the memory element. The photosensitive unit may include a second casing to which the developer cartridge is detachably attached, a photosensitive member, with which the developing agent carrier is brought into pressure contact when the developer cartridge is attached to the second casing, supported by the second casing, and a second terminal electrically connected with the first terminal when the developing agent carrier is brought into pressure contact with the photosensitive member.