Abstract: A monolithic light emitting diode array includes: at least one mixed crystal layer formed on a substrate by an epitaxial growth to provide a P-N junction at the boundary surface thereof; row of a plurality of light emitting diode portions each having the P-N junction; at least one forward mesa etching groove provided along the row of a plurality of light emitting diode portions on the at least one mixed crystal layer; a plurality of reverse mesa etching grooves provided so to be orthogonal to the at least one forward mesa etching groove and positioned between the plurality of light emitting diode portions on the at least one mixed crystal layer; a plurality of individual electrodes having electrode portions extending respectively to the plurality of light emitting diode portions so as to cross the at least one forward mesa etching groove, and a common electrode provided on a back surface of said substrate.