This article studied the leisure time behavior of undergraduate university. And the relationship between leisure time behavior and academic achievement of students in the undergraduate Naresuan university. The results of the study showed that 1) male and female students leisure time behavior. The activities of the university and faculty activities Healthy Activities And private events and more. Significant at the level of 0.05 2) students 2 and students 3 behavior, of the university and faculty activities differ significantly 0.05 .3) students who study in the fields of different leisure behavior The activity on the learning activities of the leisure activities, interaction and personal activities and so on.0.05 4) analysis of the relationship between leisure behavior and academic achievement of students found that academic achievement related to leisure behavior. Activities about learning. And the leisure activity interaction and personal activities and so on. The significant 0.05