Provided is a printing apparatus including: a photosensitive drum; a substrate including multiple formable regions in each of which corresponding one of multiple light emitting elements is formable; and a lens array, in which the substrate is arranged in a manner that a longitudinal direction of the substrate is parallel to a rotary shaft of the photosensitive drum, in which the substrate includes m formable region rows, where m is an integer number equal to or greater than 2, each of the m formable region rows including n formable regions, where n is an integer number equal to or greater than 1, arranged in a line along the longitudinal direction of the substrate, and in which one of the multiple light emitting elements formed in any one of m formable regions that are located in a predetermined column of the m formable region rows is turned on.