This study was carried out to evaluate potential of Hypsizygus marmoreus (brown cultivar) as a functional food and drug materials. H. marmoreus were divided into pileus and stipe and extracted in hot water and 80% ethanol. The total polyphenol content was highest in the hot water extracts (pileus 17.15±0.19 mg of GAE g, stipe 7.37±0.16 mg of GAE/g) and pileus compared to the ethanol extracts (pileus 10.23±0.14 mg of GAE/g, stipe 3.76.±0.19 mg of GAE/g) and stipe. Also, hot water extracts of pileus from H. marmoreus (brown cultivar) was more effective DPPH, ABTS, ORAC value, reducing power than ethanol extracts and stipe extracts. The pileus and stipe extracts were confirmed to be non-cytotoxic in the mouse macrophage cell line RAW 264.7 determined by WST-1 (4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulphonate) assay. Overall, extracts of H. marmoreus (brown cultivar) was higher antioxidant activity than other mushrooms, and no cytotoxicity. Therefore, H. marmoreus (brown cultivar) showed potential as a functional food and drug materials. The brown cultivar of H. marmoreus have higher antioxidant activity than white cultivar, H. marmoreus seem to have different antioxidant activity depending on the cultivar.