preparing a GaN substrate;

sequentially forming an active layer and a p-type nitride semiconductor layer on a surface of the GaN substrate having Ga-polarity through an epitaxial growth method;

forming a p-electrode on the p-type nitride semiconductor layer;

forming a mask on a surface of the GaN substrate having N-polarity, the mask defining a surface-irregularity formation region;

wet-etching portions of the second surface of the GaN substrate having N-polarity by using the mask as an etching mask such that standardized surface irregularities are formed; and

forming an n-electrode on the GaN substrate having the surface irregularities formed thereon,

wherein the wet-etching of the GaN substrate is performed until an end of one surface of the GaN substrate to be formed by the wet-etching using the mask meets an end of another surface of the GaN substrate to be formed by the wet-etching using the mask, the another surface being adjacent to the one surface, and

wherein when the end of one surface of the GaN substrate to be formed by the wet-etching using the mask meets the end of another surface of the GaN substrate to be formed by the wet-etching using the mask, an angle of 60 to 70 degrees is formed between the adjacent surfaces of the GaN substrate.