The purpose of this study is to analyze and understand the effect of dance class on the adolescents with developmental disability. For this, I conducted a case study. Six adolescents with developmental disability, one class teacher, and one dance class teacher were selected as the participants who could represent the characteristics of this study better. The results of this study are as follows: First, the adolescents with developmental disability were hostile to unseen teachers or others. This was a major obstacle to conducting the class. Second, the most important matter in the class for the adolescents with developmental disability was 'communication.' The most important factor for the smooth progress of the class was 'how well students and teachers would communicate each other?' The adolescents with developmental disability became to open their mind and to communicate gradually through the teachers' warm interest and concern. Third, the adolescents with developmental disability became to know the pleasure by being together. They could promote their communicating skills by doing motion plays with friends. Also they were able to have confidence and to improve their expressivity through music familiar to them. The music increased their interest and pleasure in the class.