An image forming apparatus includes a first image forming unit for forming a first developer image; a second image forming unit for forming a second developer image; a transfer unit for transferring at least one of the first developer image and the second developer image; a separation contacting unit for moving at least one of the first image forming unit and the second image forming unit to a first position and a second position; a density measurement unit for measuring a first image density and a second image density of the first developer image; and a control unit including a density calculation unit for calculating a difference between the first image density and the second image density and a density correction unit for correcting a density of the first developer image according to the difference.