Edwardsiella tarda, Streptococcus iniae and S. parauberis are main bacterial pathogens in aquaculture farms of olive flounder, Paralichthys olivaceus. We have discussed the efficacy and safety of 3 type-combined vaccines (A: S. iniae 1mg + S. parauberis 1mg + E. tarda 1mg, B: S. iniae 1mg + S. parauberis 1mg + E. tarda 0.5mg, C: S. iniae 1.5mg + S. parauberis 1.5mg + E. tarda 1mg) through intraperitoneal injections in olive flounder. None of the vaccines gave rise to any signigicant side effects on histopathology and blood chemistry. The antibody titers and lysozyme activities of A type were higher than those of B, C and control. Four weeks after vaccination, RPS (relative percent survival rates) was 62.5~75% (A type), 50~66.7% (B type) and 55.6~62.5% (C type) respectively. As the results, the combined vaccines are possible to prevent edwardsiellosis and streptococcosis, and A type : S. iniae 1mg + S. parauberis 1mg + E. tarda 1mg, is the most effective out of them.