We have investigated the flora of Daebudo Island in Ansan-si, Gyeonggi-do and Seonjaedo Island in Ongjin-gun, Incheon. Thirty-three separate field trips were carried out from March 2012 to October 2013. As a result, 518 taxa including 103 families, 316 genera, 451 species, 9 subspecies, 56 varieties and 16 forms were identified. Among them, a plant protected by the wildlife protection law, 7 Korean endemic plants and 5 threatened plants by National Arboretum and National Institute of Biological Resources were included. The floristic indicator plants were 38 taxa including 3 taxa of grade V, 4 taxa of grade IV, 4 taxa of grade III, 10 taxa of grade II and 17 taxa of grade I. Sixty-seven naturalized plants with naturalization rates of 12.9% were also found.