An image forming apparatus includes: a first unit including at least a development unit that develops an electrostatic latent image and a first developer container containing a developer; an image carrier that holds an electrostatic latent image to be developed by the development unit; a transfer unit that transfers a developer image developed by the development unit onto a recording medium; a fixing device that fixes a developer image transferred to the recording medium by the transfer unit onto a recording medium; and an image forming apparatus main body in which the first unit is installed, the image forming apparatus main body being configured such that a second unit including at least plural second developer containers respectively containing developers of different colors and development units for respective colors is installable instead of the first unit and, when the second unit is installed, a loop transport path is provided to allow the recording medium having the developer image fixed thereon by the fixing device to be transported around the second unit and toward the transfer unit.