Using the extended theory of planned behavior, this study was to analyze the effects of ethical and social perceptions, human rights perceptions, and health perceptions related to prostitution, as prerequisite variables on the attitudes and behavioral intentions of sex tourism. Structural equation model analysis and ANCOVA were performed to test hypotheses using a total of 304 valid questionnaire responses. Results showed that ethical and social perceptions and health perceptions had a significant negative effect on attitudes toward sex tourism, whereas human rights perceptions did not. It was also found that attitude and subjective norm had a significant positive effect on behavioral intentions, but perceived behavioral control did not significantly affect sex tourism intentions. In particular, it appeared that the ethical and social perception had a significant total negative effect on the intention of sex tourism. In the moderating effect analysis, using prior knowledge of prostitution-related laws, the group with high prior knowledge level had a relatively lower influence on behavior of sex tourism attitudes than the group with low level of prior knowledge. However, ANCOVA found no significant differences between the two groups, indicating that moderating effects differ by gender. This study has academic value in that it conducts an empirical study on sex tourism, a topic that is somewhat difficult to bring out in Korea. Results of this study could contribute to establishing effective policies to reduce illegal sex tourism.