Although Guleopdo is small island of only 1.71 ㎢, the endangered butterfly species, Argynnis nerippe, is abundant there. This study was carried out to estimate the abundance of A. nerippe in Guleopdo, using quadrate, mark-recapture, and line-transect methods. Although the study was insufficient, the population size was estimated at 4,467 to 6,700 larvae and approx. 1,000 adults. A. nerippe was the most abundant among butterfly species in Guleopdo, and it comprised 32% of the total butterflies. A total of 28 butterfly species were observed in this study, and 3 species of these species were migrating species. When the abundance of A. nerippe throughout the country during the period from 1938 to 2010 was studied, we found that it decreased abruptly in the 2000s. Presently, A. nerippe inhabits a few locations in the mid-northern region and western islands. The relatively high numbers of A. nerippe in Guleopdo was due to conservation of natural grasslands and grazing of livestock, which provides adequate habitat for this species.