An image forming apparatus includes development cartridges which develop an electrostatic latent image with toner, a rotary unit provided with the developing cartridges, an intermediate transfer belt which receives the toner image, and a controller. A length of the intermediate transfer belt is set such that a length of the image forming region is corresponded to a length of a set recording medium having a predetermined size and a length of the non-image forming region is corresponded to a distance between a rear end of the preceding one of the set recording mediums and the front end of the subsequent one. A rotational movement period of the intermediate transfer belt corresponding to the length of the non-image forming region is equal to or greater than a time required for switching the developing cartridges. The controller performs an switching operation of the developing cartridges in accordance with a size of a recording medium.