It is well known that autistic disorder has serious problems in developing object relations. However research that can help autistic disorder to de velop object relations is in its early stage. The purpose of the present study was to investigate how art therapy using plastic activity affects object relations(play. personal relations. behavior) of autistic disorder. Two children with autistic disorder. who had problems in developing normal object relations served as subjects. Their chronological age were 6. Prior to therapy. they had not played with other children and rarely showed spontaneous act. Both children participatened in plastic activity and drawing weekly for 6 months. Each session lasted approximately 50 minutes. They were diagnosed as ha ving autistic disorder based on the Childhood Autism Rating Scale (CAR S). Their object relations for pre and post-test were evaluated using EHWA-Check List for Autistic Children (E-CLAC) and Kinetic-House-Tree- Person( K-HTP) and ratings of their mother and teacher. E-CLAC items used in the present study were play. personal relations. following instructions. behavior. The therapeutic effects were evaluated using a pre/post→test design. For each child. the therapeutic procedure and results were described for each session. Through the above mentioned procedures following conclusions were drawn First. the art therapy using plastic activity ímproved the two children\'s relationship with other children and adults and increased the numher of plays they participated in. Second. the art therapy using plastic activity improved the children’ s relationship with their parents. siblings and other children. Finally. the art therapy using plastic activity increased following instructions. spontaneity. concentration and spontaneous behavior 1n addition. the object relations of the autistic disorders were discussed.