We investigated the species richness of lepidopteran insects (excluding butterflies and microlepidoptera) of Mt. Seungdal-san, Muan-gun, Jeollannam-do, Korea, from 2003 to 2005 using two portable light traps. A total of species comprised 423 species belongs to 17 families were identified. The family Noctuidae with 209 species was dominant in the area followed by Geometridae with 132 species. Based on the number of individuals collected, Geometridae was the highest mostly due to an ennomine species (Alcis angulifera). Monthly fluctuations of moth species richness present an M-shaped curve with two high peaks at June and August. Comparisons of species diversity of yearly captures revealed that the diversity of 2003 was higher than that of 2004, but the diversities of between 2003 and 2005, and between 2004 and 2005 were no different.