The purpose of this study is to improve the level of adjustment behaviors through the gameplay therapy in the form of structured group activities aiming at self-control, communication, problem solving, and soci ali zation of a child who is irritable, lacks self control, self-confidence, and has difficulties in social adaptation due to his loss of parents and environmental characteristics of institution. Gameplay therapy is adequate for the developmental level of school age children and it promotes communication, provides opportunities for acquiring new informations and experiments of new roles and behaviors, and includes social process of making participants to fit into its social needs and norms. And through this, the child who is institutionalized can promote his abilities of working through his painful experiences like loss, grief, rejection and abused memories, of problem solving and adaptation to his enviromnents through his socialization experience in group activities as well as promote his level of self-esteem. So, gameplay therapy is effective in improving abilities of coping and adaptation for environments of children. The issue of this study is to investigate the effects of play therapy using games on the change of adaptative behaviors of institutionalized child. The significant results are as follows: 1. The subject could achieve the appropriate verbal expression levels adequate his situations in play sessions, control his emotion, maintain his positive interactions with peers, and the whole interactions among group members were increased as the treatment went to the latter half. 2. the scores of co-operation, assertiveness, and self-regulation were improved in Social Function Assessment Scale, the level of interaction with group members showed increas in :MIM assessment, and the total adjustment behavior showed improvement positively in Adjustment Behaviors Test and K-CBCL results. 3. The subject manages himself well with his responsibilities in the institution, participates actively most of the activities in his enviromnents and showed increased caring behavior for youngsters.