This study examines in fast food consumers' perceived risk, purchase intension and its effect on risk reduction behavior. According to the results, factors of perceived risk are 6 (social, physical, financial, temporal, efficiency, psychological). Physical risk has perceived more to women than men, but financial risk has perceived more to men than women. And teenagers perceived more physical risk than twenties although it's not difference for use frequency of fast food. Repondents have perceived risk for fast food use regardless of it's use frequency. Fast food heavy users have felt more psychological risk than light users. And respondents who have perceived more physical risk were low attitude to product, nutrition, and purchase intention. The factors of risk reduction behavior were 2 (image, well-being seeking), repondents who have perceived physical risk have marked tendency of risk reduction behavior. Specially, respondents had strongly information desire regarded to fast food for risk reduction. Thus, it is need open for fast food information, development of well-being menu, advertising and PR strategy for perceived risk reduction. In consumer behavior, physical risk was very sensitive and tendency of risk reduction behavior showed clearly.