We investigated the antioxidative effects of solvent extracts of doenjang fermented using Bacillus subtilis DJI (DJI doenjang) in vitro. The solvents used for extraction were ethanol, n-hexane, and water. The antioxidative activities of DJI doenjang solvent extracts were measured by estimation of peroxide value, the presence of linoleic acid level, and nitrite scavenging activity, the Rancimat test, and 1,1-diphenyl-2-picryl hydrazyl (DPPH) free-radical generation, in comparison with the commercial antioxidant butylated hydroxytoluene (BHT). The peroxide value of an ethanol extract was lower than those obtained using n-hexane and water extracts. Furthermore, the peroxide value of the ethanol extract was similar to that obtained after BHT treatment. The nitrite scavenging activity was 23.36% after addition of 600 ppm DJI doenjang ethanol extract, and the DPPH free-radical scavenging activity was 19.06% under same condition, which shows that DJI doenjang ethanol extract exhibited lower antioxidative capacities than did BHT. In the Rancimat test, the ethanol extract (11.20 min induction time), n-hexane extract (7.58 min induction time), and water extract (8.26 min induction time) after treatment with 600 ppm DJI doenjang extracts demonstrated longer induction periods than did BHT (6.94 min). These results indicate that DJI doenjang has potential anti-oxidative activity.