A lighting apparatus comprising: an elongated flat substrate; a plurality of semiconductor light sources arranged on the flat substrate at a predetermined interval in a longitudinal direction of the flat substrate; a lens plate disposed to face the semiconductor light sources, the lens plate including a lens-light-incident surface and a lens-light-emitting surface, light emitted by the semiconductor light sources being incident into the lens-light-incident surface, a lens thickness being defined between the lens-light-incident surface and the lens-light-emitting surface; a base frame engaging with the lens plate so that the flat substrate is disposed between the lens plate and the base frame; a first lens section formed on one of the lens-light-incident surface and the lens-light-emitting surface and configured to distribute the light emitted by the semiconductor light sources in the longitudinal direction; and a second lens section formed on the other one of the lens-light-incident surface and the lens-light-emitting surface and configured to distribute the light emitted by the semiconductor light sources in a width direction which is orthogonal to the longitudinal direction, characterized in that the first lens section includes a plurality of curvature surface units, a) each curvature surface unit corresponding to each semiconductor light source, and b) each of the curvature surface units including a plurality of convex section curvature surfaces (8A, 8B) having different curvature radii and formed adjacent in the longitudinal direction, and c) each of the curvature surface units being disposed inside an area of either the lens-light-incident surface or the lens-light-emitting surface on which the first lens section is formed, said area opposing an area corresponding to a width of the corresponding semiconductor light source in the longitudinal direction. an elongated flat substrate; a plurality of semiconductor light sources arranged on the flat substrate at a predetermined interval in a longitudinal direction of the flat substrate; a lens plate disposed to face the semiconductor light sources, the lens plate including a lens-light-incident surface and a lens-light-emitting surface, light emitted by the semiconductor light sources being incident into the lens-light-incident surface, a lens thickness being defined between the lens-light-incident surface and the lens-light-emitting surface; a base frame engaging with the lens plate so that the flat substrate is disposed between the lens plate and the base frame; a first lens section formed on one of the lens-light-incident surface and the lens-light-emitting surface and configured to distribute the light emitted by the semiconductor light sources in the longitudinal direction; and a second lens section formed on the other one of the lens-light-incident surface and the lens-light-emitting surface and configured to distribute the light emitted by the semiconductor light sources in a width direction which is orthogonal to the longitudinal direction, a) each curvature surface unit corresponding to each semiconductor light source, and b) each of the curvature surface units including a plurality of convex section curvature surfaces (8A, 8B) having different curvature radii and formed adjacent in the longitudinal direction, and c) each of the curvature surface units being disposed inside an area of either the lens-light-incident surface or the lens-light-emitting surface on which the first lens section is formed, said area opposing an area corresponding to a width of the corresponding semiconductor light source in the longitudinal direction.