A light emitting device comprising: a metal reflective layer comprising a phase modulation surface; a first electrode disposed on the phase modulation surface of the metal reflective layer; a second electrode disposed to oppose the first electrode; and a light emitting structure disposed between the first electrode and the second electrode to form a micro cavity having a resonance wavelength, wherein the phase modulation surface comprises a plurality of nano light resonance structures, the plurality of nano light resonance structures being column type magnetic resonators in which a magnetic field component of incident light resonates at a periphery of nano scale patterns, and wherein the resonance wavelength of the micro cavity is determined according to a phase delay caused by the plurality of nano light resonance structures and an optical distance between the metal reflective layer and the second electrode; wherein the first electrode is a transparent electrode, wherein a lower surface of the metal reflective layer is flat; wherein the phase modulation surface of the metal reflective layer is disposed to face the first electrode; and wherein a lower surface of the first electrode has a protruding pattern that is complementary to the phase modulation surface and an upper surface of the first electrode is flat, characterized in that the second electrode includes a reflective metal material that reflects light and has a thickness of 50 nm or more and in that the metal reflective layer has a transflective property so that the metal reflective layer reflects a part of light and transmits the remaining part of the light, the thickness (t) between the bottom of a peripheral space of each of the nano light resonance structures and a lower surface of the metal reflective layer being 10 nm to 20 nm. a metal reflective layer comprising a phase modulation surface; a first electrode disposed on the phase modulation surface of the metal reflective layer; a second electrode disposed to oppose the first electrode; and a light emitting structure disposed between the first electrode and the second electrode to form a micro cavity having a resonance wavelength, wherein the phase modulation surface comprises a plurality of nano light resonance structures, the plurality of nano light resonance structures being column type magnetic resonators in which a magnetic field component of incident light resonates at a periphery of nano scale patterns, and wherein the resonance wavelength of the micro cavity is determined according to a phase delay caused by the plurality of nano light resonance structures and an optical distance between the metal reflective layer and the second electrode; wherein the first electrode is a transparent electrode, wherein a lower surface of the metal reflective layer is flat; wherein the phase modulation surface of the metal reflective layer is disposed to face the first electrode; and wherein a lower surface of the first electrode has a protruding pattern that is complementary to the phase modulation surface and an upper surface of the first electrode is flat, characterized in that the second electrode includes a reflective metal material that reflects light and has a thickness of 50 nm or more and in that the metal reflective layer has a transflective property so that the metal reflective layer reflects a part of light and transmits the remaining part of the light, the thickness (t) between the bottom of a peripheral space of each of the nano light resonance structures and a lower surface of the metal reflective layer being 10 nm to 20 nm.