The purpose of this study was to examine the mediating role of post-event rumination in the relationship between evaluative concerns perfectionism and social anxiety as well as between intolerance of uncertainty and social anxiety. A total of 369 undergraduate and graduate students were asked to complete the questionnaires, including the Evaluative Concerns Perfectionism Scale, Intolerance of Uncertainty Scale-12, Post-Event Rumination Scale, Social Interaction Anxiety Scale, Social Phobia Scale, and short form of the Korean version of Center for Epidemiologic Studies Depression Scale(CES-D). The results of this study were as follows: First, all variables were significantly positively correlated. After controlling for depression, the variables were still significantly positively correlated. Second, post-event rumination partially mediated the relationship not only between evaluative concerns perfectionism and social anxiety but also between intolerance of uncertainty and social anxiety. After controlling for depression, the mediation effect of post-event rumination was still significant. Finally, clinical implications and limitations of this study were discussed.