1. A printing apparatus comprising: a transport unit that transports a transparent medium and winds the medium subjected to printing in a roll shape; a first nozzle line in which a plurality of nozzles ejecting ink to form a color image are arranged; and a second nozzle line in which a plurality of nozzles ejecting ink to form a background image are arranged; wherein when a plurality of printed images to be formed by overlapping the color image and the background image continue to be printed on the medium and when the background image of the printed image is located on the outside of the color image in a case where the medium is wound in the roll shape, a confirmation image formed by overlapping the color image and the background image is printed on an end portion of the medium to be wound in the roll shape so that at least a part of the color image is located on the outside of the background image.