The purpose of this study was to examine the mediating effect of social support on the relationship between social and psychosocial stress and depression of college students. The survey was based on an online survey of 176 university students in D metropolitan City using a self-administered questionnaire during the period from September 1 to October 30, 2021. As a result of the study, the higher the psychosocial stress, the higher the depression (p<0.001), while the lower the social support, the higher the depression (p<0.001) of the study subjects. In the correlation between depression and psychosocial stress and social support of the study subjects, depression showed a significant positive correlation with psychosocial stress (r=0.648, p<0.01), while a significant negative correlation with social support (r=-0.215, p<0.05). As a result of verifying the mediating effect of social support in the relationship between psychosocial stress and depression of the study subjects, it was found that social support plays a partial mediating role between psychosocial stress and depression (Z=-5.28, p<0.01). These results suggest that social support of college students may have a mediating effect on relieving psychosocial stress related to depression.