An image forming apparatus according to the invention includes a plurality of image forming units and a changeover unit. The plurality of image forming units form multicolor images on an image carrier by overlapping, on a medium, developer images developed using developers. The changeover unit changes a layer overlapping sequence of the developer images on the medium. The developers include a developer emitting light according to radiation of non-visible light, and the changeover unit changes the layer overlapping sequence of the developer images using the developer emitting the light according to radiation of the non-visible light.