An image forming apparatus includes an image carrier unit, a developing device, a unit support frame, a retainer, and a developing device moving mechanism. The retainer swings in a first direction, in which the image carrier unit and the developing device are mounted in the unit support frame, to perform positioning of an image carrier, and swings in a second direction, in which the image carrier unit and the developing device are drawn out from a main body of the image forming apparatus, to unlock a positioned state of the image carrier. The developing device moving mechanism associates with the swing of the retainer in the first direction to dispose the developing device at a developing position, and associates with the swing of the retainer in the second direction to dispose the developing device at a separation position.