From 2008 to 2009, the stem rot of Astragalus sinicus L. caused by Sclerotium rolfsii occurred sporadically in Gyeongnam area, Korea. The typical symptom is water-soaking, rotting and wilting on the stem. The infected plants were eventually died. White mycelial mats were spread over lesions, and then sclerotia were formed on stems and near soil line. The sclerotia were globoid in shape, white to brown in color, 1-3 mm in size and the hyphal width was 3-9 μm. The optimum temperature for mycelial growth and sclerotial formation on PDA was 30oC. The typical clamp connections were observed in the hyphae of the fungus grown on PDA. On the basis of mycological characteristics and pathogenicity to host plants, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report on the stem rot of A. sinicus caused by S. rolfsii in Korea.