A holding frame of a lens unit has a frame main body of a cylindrical shape, which corresponds to the shapes of lenses. A protruding part is provided at a front end of the frame main body. The protruding part protrudes to the inside of the frame main body. The thickness of the protruding part is the same as that of a flange portion of a first lens. When the first lens is fitted into a space formed by the protruding part, a front surface of the flange portion of the first lens is flush with a front surface of the protruding part. A first light shielding film, which functions as an aperture stop, is affixed to at least one of the flange portion of the first lens and the front surface of the protruding part.