The purpose of this study is to analyze the theme of Joseph Campbell's hero-myth demonstrated in the Sandplay therapy with which 8-year-old boys are treated. Using the case of Sandplay therapy for an 8-year-old boy, this study looked at the hero-myth with narrative hermeneutics to reconstruct the themes of departure, initiation, and return which are usual in hero-myth shown in children's Sandplay therapy. The narrative is reconstructed based on the hero-myth. The departure process consists of ‘the boy becoming lost and shivering with cold’, ‘finding the treasure map’, and ‘preparing for adventure’. The initiation process includes ‘entering the adventurous world’, ‘encountering monsters and assistants’, and ‘slaying monsters and discovering a golden mountain’. Lastly, the return process covers ‘returning home after the adventure’ and ‘the boy arriving home’. The research results tell us that the Sandplay therapy is not only the therapy for the children to be healed and matured, but also mythical in itself. The meanings and implications of the results are also discussed.