Our country has entered upon the era of 13 million oversea travellers, greeting 21st century. This study attempts to examine how much the travel agent's brand equity and perceived risk impact on post purchase doubt when oversea travellers choose the package tour. This research problem starts from intangibility of oversea tours and the fact that travellers can't experience the quality of package tour until participating. 200 questionnaires were collected for the empirical study to the people who travelled overseas during the last 3 years. Among them, 194 questionnaires were used for the final analysis. The respondents consist of 40.7% males and 59.3% females. The multiple regression analysis shows that travel agent's image, package tour perceived quality and travel agent's loyalty influence on post purchase doubt as variables in order(p<.05). And this study also shows that perceived risk influences on post purchase doubt(p<.05). And I investigated the demographics of oversea travellers and intergroup differences according to the purchasing situations for the development of market segmentation strategy of travel agent (T-test & ANOVA). The result shows that there is a significant difference depending on the gender of purchaser and the size of travel agent. But the age of purchaser, type of tour, etc. have statistically no significant differences.