Mitigation measures in EIS are the important factors in the effectiveness of EIS. This paper analyzed the content of mitigation measures described in the 30 EISs selected, using 7 analysis items in order to discover the degree of effectiveness of mitigation measures. 30 EISs used in this study were selected through variance maximization strategy, and the 7 analysis items were; 1) thoroughness of mitigation content, 2) quantification of mitigation content, 3) explicit description of mitigation effect, 4) likelihood of mitigation effect, 5) impacted area of mitigation effect, 6) time frame of mitigation effect, and 7) environmental impact of mitigation measures. The results showed that the effectiveness of mitigation measures in the analyzed EISs was relatively low both in the appropriateness and in the specificity. It was suggested that in order to improve the appropriateness of EIS as a decision making tool, the effect of mitigation measures, as well as the mitigation measures themselves, should be studied and described more thoroughly and specifically.