An image forming apparatus includes a main frame and a unit installable in an installation position in the main frame. The main frame has a first guide, a second guide, a groove, and a frame-side connector. The frame-side connector is movably held by the main frame. The unit has a first reference portion and a unit-side connector. The unit is installed in the main frame by a first process in which the first reference portion is guided by the first guide, a second process, in which the first reference portion is guided by the second guide, and a third process, in which the first reference portion is received in the groove and the unit is located in the installation position. The unit-side connector engages the frame-side connector in the first process, and the frame-side connector moves as the unit-side connector moves in the second process and in the third process.