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 WE examined. Six CKJ simples were evaluated and 3 were selected based on the results of the physicochemical analysis and sensory evaluation for further antioxidant study. IC50 for DPPH scavenging activity or methanol extracts of CKJ ranged from 238.1 to 345.7 μg/mL. CKJ exhibited over 80% scavenging of ·OH and ONOO- at concentrations of 100 μg/mL and 250 μg/mL, respectively. O2- and NO scavenging activities of three CKJ were increased in a dose dependent manner with the concentration tested from 100 to 1000 μg/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, O2-, and nitrite radical were rather moderate. In conclusion, CKJ may reduce the oxidative stress in the body by scavenging the free radicals.