A hole that penetrates each light emitting diode board in the thickness direction of the board is provided, on one end portion in the longitudinal direction of each of a plurality of light emitting diode boards which have a plurality of light emitting diodes mounted on one surface, respectively have substantially a strip shape, and are arranged in a plurality of rows. The board holder has: protruding sections which are inserted into the holes of the adjacent light emitting diode boards; and a coupling section which is disposed in the direction orthogonally intersecting the longitudinal direction of the light emitting diode board, has a strip-shape, and couples respective base ends of the protruding sections. The plurality of light emitting diode boards disposed in parallel are held by inserting the protruding sections into the holes.