To further the goal of isolating Bacillus sp. from commercial chungkukjang (CKJ) for a development of a probiotic dietary adjunct using soymilk or milk, antioxidant activity of CKJ purchased from the Sunchang Traditional Village in Chunbook province was examined. Six CKJ samples were evaluated and 3 were selected based on the results of the physicochemical analysis and sensory evaluation for further antioxidant study. $IC_{50}$ for DPPH scavenging activity of methanol extracts of CKJ ranged from 238.1 to 345.7 ${mu}g/mL$. CKJ exhibited over 80% scavenging of ${cdot}OH$ and ONOO- at concentrations of 100 ${mu}g/mL$ and 250 ${mu}g/mL$, respectively. $O_2^-$ and NO scavenging activities of three CKJ were increased in a dose dependent manner with the concentration tested from 100 to 1000 ${mu}g/mL$. In this study, the methanol extract of CKJ exhibited a great reduction capability and powerful free radical scavenging activity, especially against OH. and ONOO-, which are the most toxic radicals responsible for oxidative damage in the body. However, radical scavenging effects of CKJ on DPPH, $O_2^-$, and nitrite radical were rather moderate. In conclusion, CKJ may reduce the oxidative stress in the body by scavenging the free radicals.