This study was is to establish the floristic composition of vascular plants of Sinan-gun, Korea. The field works performed 26 times from April to November in 2010. Vascular plants observed were 768 taxa containing 118 families, 428 genera, 674 species, 1 subspecies, 81 varieties and 12 formae. Among the investigated plants, 13 taxa (2.4%) were Korean endemic. The rare plants designated by the Korea Forestry Service in this region were 27 taxa. The floristically and geographically important plants were 112 taxa: grade I, II, III, IV, and V species were 68, 7, 26, 3, and 8 taxa, respectively. In the 321 naturalized plants in Korea, 78 taxa (24.3%) were found in this region and it is relevant to 10.2% of the total taxa number of this region. As a endangered species designated by the Ministry of Environment of Korea, we report Millettia japonica (grade II) in this region.