A lens unit includes a lens holder having an opening and an inner wall, the lens having an optical axis passing through the opening, a first lens having a outer circumference, and arranged in the lens holder along the optical axis, a second lens having a outer circumference, and arranged in the lens holder along the optical axis, and three strut portions provided on the inner wall of the lens holder. The strut portions position the first lens and the second lens. The strut portions have surfaces facing the optical axis, respectively, the surfaces of the strut portions slanting with respect to the optical axis and contacting the outer circumferences of the first lens and the outer circumferences of the second lens. This lens unit have the lenses positioned accurately.