Previous studies have shown that two types of private self-consciousness result in opposing effects on depression; one of which is self-rumination, which leads to maladaptive effect, and the other is self-reflection, which leads to an adaptive effect. Although a number of studies have examined the mechanism of the maladaptive effect of self-rumination, only a few studies have examined the mechanism of the adaptive effect of self-reflection. The present study examined the process of how self-reflection affected depression adaptively. Based on the previous findings, we proposed a hypothetical model assuming that hardiness acts as a mediator of self-reflection. To test the validity of the model, structural equation modeling analysis was performed with the cross-sectional data of 155 undergraduate students. The results suggest that the hypothetical model is valid. According to the present results and previous findings, it is suggested that self-reflection is associated with low levels of depression and mediated by “rich commitment”, one component of hardiness.