A lens unit includes a lens array, a first light blocking member, and a second light blocking member. The lens array includes a plurality of lens pairs arranged in a substantially linear arrangement. Each of the lens pairs includes a first lens for forming an inverted reduced-size image of an object and a second lens for forming an inverted enlarged-size image of the inverted reduced-size image. The first light blocking member is disposed between the first lenses and the second lenses, and includes first apertures. The second light blocking member includes second apertures arranged in a substantially linear arrangement corresponding to an arrangement interval of the lens pairs, and having different opening portion shapes depending on a position of the lens pairs in an optical axis direction of the lens pairs. The second light blocking member is disposed at least between the first lenses and an object plane or the second lenses and an image plane.