Non-native flora of the Ulleung island, located in the eastern part of South Korea, was surveyed as 54 taxa with 16 families, 35 genera, 53 species and 1 variety. Considering the geographical distribution aspects of the island, the flora of the island showed more closely related with Korean Peninsular than Japan. Poaceace (28%) and Asteraceae (24%) represents more than 50% of the non-native flora in Ulleung island, meaning that they have an advantage of seed dispersal and adaptation to new environments. Ulleung island is comparatively small island of vulnerable to the attack of invasive alien plants but presently, it has the least number of non-native plants than other areas in South Korea. Therefore, we need to take much interest in prevention and mitigation of non-native plant in the future.