We examined the effect of the factors of hesitancy toward and the motivation for self-disclosure on loneliness using the postulated model: hesitancy toward and motivation for self-disclosure → self-disclosure → loneliness. Five scales about self-disclosure and loneliness were administered to 235 junior high school students. Findings suggest that release of one's feelings strongly promotes self-disclosure and anxiety about the target causes hesitancy toward engaging in selfdisclosure; hesitancy toward personal or private self-disclosure also has an effect on loneliness.There have been many studies about self-disclosure in social psychology or clinical psychology. Self-disclosure refers to the process by which individuals reveal personal thoughts, feelings, and experiences to other people (Reis, 2000). Self-disclosure has been one of the most commonly studied features of relationship developments. The importance of disclosing personal and intimate information about oneself has been emphasized in the context of friendship formation and good health. For a person who is in a negative condition, self-disclosure is especially effective in improving both mental and physical health.While self-disclosure has been found to have positive effects, some effects have also been found to be negative. Hatfield (1984) listed negative effects of selfdisclosure as follows: fear of exposure, fear of abandonment, fear of angry attacks, fear of loss of control, fear of one's own destructive impulses, and fear of losing one's individuality. Disclosing negative information sometimes has an