A semiconductor light emitting device comprising: a substrate; a first conductivity type semiconductor layer on the substrate; an active layer on the first conductivity type semiconductor layer; a second conductivity type semiconductor layer on the active layer; a first electrode under the first conductivity type semiconductor layer, the first electrode comprising a pattern having a predetermined shape; a nitride semiconductor layer between the substrate and the first conductivity type semiconductor layer, wherein the pattern of the first electrode is embedded in the nitride semiconductor layer, wherein the nitride semiconductor layer comprises at least one of a buffer layer comprising groups III-V compound semiconductors and an undoped semiconductor layer, wherein a thickness of the first electrode is greater than a thickness of the nitride semiconductor layer, wherein the first conductivity type semiconductor layer is formed on the first electrode and the nitride semiconductor layer; a first electrode pad electrically connected to a top of the pattern of the first electrode; and a second electrode unit on the second conductivity type semiconductor layer, wherein a lower part of the first conductivity type semiconductor layer is formed in gaps of the pattern of the first electrode on the nitride semiconductor layer, wherein the first electrode is electrically connected to a lower part of the first conductivity type semiconductor layer, wherein the first electrode pad is formed on the first electrode, characterized in that the lower part of the first conductivity type semiconductor layer and a part of the pattern of the first electrode are exposed, and the first electrode pad is formed on the first electrode and the exposed lower part of the first conductivity type semiconductor layer, and in that the second electrode unit comprises: a second electrode layer on the second conductivity type semiconductor layer; a second electrode pad electrically connected to the second electrode layer and the second conductivity type semiconductor layer; and a second electrode branching from the second electrode pad in branched pattern shapes, wherein the second electrode pad is formed on the second electrode layer, wherein the second electrode branched from the second electrode pad is formed on the second electrode layer. a substrate; a first conductivity type semiconductor layer on the substrate; an active layer on the first conductivity type semiconductor layer; a second conductivity type semiconductor layer on the active layer; a first electrode under the first conductivity type semiconductor layer, the first electrode comprising a pattern having a predetermined shape; a nitride semiconductor layer between the substrate and the first conductivity type semiconductor layer, wherein the pattern of the first electrode is embedded in the nitride semiconductor layer, wherein the nitride semiconductor layer comprises at least one of a buffer layer comprising groups III-V compound semiconductors and an undoped semiconductor layer, wherein a thickness of the first electrode is greater than a thickness of the nitride semiconductor layer, wherein the first conductivity type semiconductor layer is formed on the first electrode and the nitride semiconductor layer; a first electrode pad electrically connected to a top of the pattern of the first electrode; and a second electrode unit on the second conductivity type semiconductor layer, wherein a lower part of the first conductivity type semiconductor layer is formed in gaps of the pattern of the first electrode on the nitride semiconductor layer, wherein the first electrode is electrically connected to a lower part of the first conductivity type semiconductor layer, wherein the first electrode pad is formed on the first electrode, characterized in that the lower part of the first conductivity type semiconductor layer and a part of the pattern of the first electrode are exposed, and the first electrode pad is formed on the first electrode and the exposed lower part of the first conductivity type semiconductor layer, and in that the second electrode unit comprises: a second electrode layer on the second conductivity type semiconductor layer; a second electrode pad electrically connected to the second electrode layer and the second conductivity type semiconductor layer; and a second electrode branching from the second electrode pad in branched pattern shapes, wherein the second electrode pad is formed on the second electrode layer, wherein the second electrode branched from the second electrode pad is formed on the second electrode layer.