The purpose of this study is to investigate how residents' benefits, attachment and support for the Expo 2012 Yeosu Korea are related to Expo event impacts. For the purpose of applying the social exchange theory as a theoretic basis of this study to effects on event and changes of the perception of residents, related literatures and previous studies were reviewed. To summarize the findings of the analysis, there were six factors in the perception toward effects of the Expo 2012 Yeosu Korea (negative environmental impact, positive economic impact, positive social-cultural impact, negative social-cultural impact, positive environmental impact and negative economic impact), while factors of residents’ perception toward the development were classified into three(residents’ benefit, attachment, and support for Expo). A factor analysis was used to delineate underlying dimensions of Expo event impacts and regression analysis was used to investigate relationship between Expo event impacts and support. The result of regression analysis indicated that positive economic impact, positive social-cultural impact and positive environmental impact had an effect on residents' benefits and positive social-cultural impact, positive environmental impact and negative economic impact had an effect on residents' attachment. Furthermore, this study support well the social exchange theory because residents' benefits and attachment had a strong effect on their support for the Expo event.