Abstract: A simple and inexpensive planar lighting device realizing a high luminance is provided, including: a light guide plate having a pair of opposite light entry faces, a light emitting face extending perpendicularly to the light entry faces, a plurality of hemispherical surfaces formed on the light emitting face, and a light non-emitting face opposite to the light emitting face; a light source disposed to extend along each of the light entry faces; a reflector for reflecting light from the light source toward a respective one of the light entry faces; a reflecting plate disposed to extend along the light non-emitting face for reflecting light leaking from the light guide plate toward the light guide plate; and a lens sheet disposed to extend along the light emitting face and formed with a plurality of first ridges extending parallel with the light entry faces on a face thereof opposite to the light emitting face, the first ridges each having a triangular section.