The present studies investigated the relation between subcategories of positive beliefs about depressive rumination (beliefs about the advantages of ruminating and the disadvantages of not ruminating) and depressive rumination. The authors conducted three questionnaire studies with undergraduate students. Based on factor analyses, the Reasons for Rumination Inventory (RRI) was developed. The RRI consisted of four factors concerning the advantages of ruminating (Insight into Oneself and Situations, Preparation for Future Catastrophes, Increase of Empathy, and Prevention and Decrease of Dysphoria), and of three factors concerning the disadvantages of not ruminating (Avoidance of Future Mistakes, Avoidance of Persistence and Exacerbation of Dysphoria, and Avoidance of Negative Influence on Personality and Situations). Correlations among the subscale scores on the RRI and measures of positive beliefs about worry showed moderate validity of the RRI. The test-retest correlations demonstrated adequate reliability of the RRI. Additionally, results of correlation analyses showed that the Insight into Oneself and Situations were related to depressive rumination. All factors of beliefs about the disadvantages of not ruminating were also related to depressive rumination. These results indicated that the intention of understanding oneself and one's situations, and intention of avoiding negative consequences without ruminating were associated with persistence of depressive rumination.