This study was conducted to examine whether coping flexibility act as mediator between rumination and perceived stress. The Coping Flexibility Questionnaire, Perceived Stress Scale, Korean-Ruminative Response Scale were administrated in 331 university students from 5 universities in Chung-Buk. Descriptive statistical analysis, correlation analysis, and hierarchical analysis were conducted on the collected surveys using the statistics program SPSS 18.0 version. As a result, first, significant correlations among variables were found. Second, coping flexibility partially mediated the relationship between rumination and perceived stress. Results showed that perceived coping resources and flexibility in coping behavior, which are sub-factors of coping flexibility, mediated the relationship between rumination and perceived stress, but the coping behavior evaluation which is sub-factor of coping flexibility has not a significant mediating effect on the relationship between rumination and perceived stress. The results of this study, suggest that improving coping flexibility can be effective for reduce ruminations to perceived stress.