Antioxidative activities of various enzymatic extracts from Inonotus obliquus were evaluated by measuring 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, and alkyl radical-scavenging activities using electron spin resonance spectrometer. The mushrooms were enzymatically hydrolyzed by seven carbohydrases (Viscozyme, Celluclast, Dextrozyme, AMG, Promozyme, Maltogenase, and Termamyl) and eight proteases (${alpha}$-chymotrypsin, Alcalase, Flavourzyme, Neutrase, papain, pepsin, Protamex, and trypsin). Celluclast and Protamex extracts showed the highest DPPH radical-scavenging activities, and $IC_{50}$ values were 0.155 and 0.151 mg/mL, respectively. All enzymatic extracts of I. obliquus had scavenging potencies to hydroxyl radical, and $IC_{50}$ value of the pepsin extract with the highest activity was 0.847 mg/mL. Maltogenase and trypsin extracts showed the highest scavenging activities on alkyl radical, and $IC_{50}$values were 0.082 and 0.094 mg/mL, respectively. The pepsin extracts showed protective effect on $H_2O_2$-induced DNA damage. In addition, the pepsin extracts decreased generation of reactive oxygen species and cell death in PC-12 cells against $H_2O_2$-induced oxidative damage. The findings of the present study suggest that the enzymatic extracts of I. obliquus have antioxidative activity against oxidative stress on PC-12 cells.