The aim of this study was to identify chemical composition and antioxidant activity of phenolic extract of fruiting bodies of an artificially cultivated Hankyong Sanghwang mushroom, Phellinus linteus KACC 93057P (PLHS). The total phenolic content of 60% ethanolic extract of fruiting bodies of two-year-old PLHS grown on Oak wood logs was 19.05±0.32 mg gallic acid equivalent (GAE)/g, which was 4-10 times high compared to the other species of mushrooms. 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbisthiazoline-6-sulfonic acid) (ABTS) radical scavenging activities and the ferric reducing antioxidant power (FRAP) value of PLHS were 2-10 and 5 times higher, respectively, than those of the other species of mushrooms. High performance liquid chromatography (HPLC) analysis of ethyl acetate fraction of 70% methanolic extract of the fruiting bodies of PLHS revealed the presence of styrylpyrone-class compounds, davallialactone, hispidin, hypholomine B, and caffeic acid, a compound of the phenylpropanoid pathway.