The purpose of this study was to investigate the effectiveness of sandtray therapy for improving the interpersonal relationship of bullied children. The subjects of this study were 20 boys (9 years old) who had difficulty in interpersonal relationship because of bullying victims, and the sandtray therapy from April 8, 2017 to December 4, 2017. First, is there an effect on pre-post-interpersonal relationship improvement of interpersonal scale of bully victims? Second, what is the pre-post-change of HTP picture test? Third, what is the pre-post-change of sandtray therapy? First, the interpersonal scale was used as a self-report questionnaire for the relationship change scale developed by Moon, Moon(1980). Second, we investigated the changes of children through HTP picture test. Third, the sandtray therapy process was developed through Dora Kalff s developmental stages, struggle stage, and adaptation process. As a result of the study, pre-and post-test scores of children with bullying victims were improved. In other words, in stage 1~3 of the animals and plants, he was confused and treated the rough and wild sand to express his negative feelings and anger toward his father and his friends. During the struggle phase 4-13, confusion persisted or the figure was roughly handled, showing the role of the opposite pole. With the advent of full-scale construction equipment from the 14th session, the sandbox began to feel more structured and as it was approaching the end, it began to adapt, including playing with friends and inviting peers at home.