An image forming apparatus to which a cartridge including first and second cartridge contacts is detachably mountable, includes: a guiding member for guiding the cartridge to a positioning portion provided in a main assembly of the image forming apparatus; a first main assembly contact contactable to the first cartridge contact when the cartridge is positioned partway toward the positioning portion and is positioned in the positioning portion; a second main assembly contact contactable to the second cartridge contact when the cartridge is positioned partway toward the positioning portion; a third main assembly contact contactable to the second cartridge contact only when the cartridge is positioned in the positioning portion; and a control portion for detecting presence or absence of the cartridge in the main assembly and a mounted state of the cartridge by being electrically connected with the first, second and third main assembly contacts.