A purpose of this study is to certify that Art therapy can alleviate ADHD(Attention Deficit Hyperactivity Disorder) children\'s aggression and help them concentrate their attention. For this, we chose subjects that were freshmen in the elementary school, who had taken after-school classes. This study was conducted 18 times overall. Each research took forty or sixty minutes once a week and lasted from October, 2004 to May, 2005. Art therapy program consists of three steps and it was organized structured or unstructured depending on each situation. Its expression method is a free drawing and the material is clay that children are fond of. That\'s because ADHD children can erupt their aggressive energy by slapping and fumbling clay. We expected them to dissolve their oppressed emotion and conflict and then, to undergo a positive emotional change through their pleasure and familiarity which they can feel on the edge of their fingers with clay. We evaluated subjects before and after the therapy and compared with each other by using K-CBCL(Korean Child Behavior Checklist) test. As a result, the modeling activity, one of the art therapies helped ADHD children elevate their accomplishment and self-esteem and also stabilize their mental state. Thus this fact could affect ADHD children\'s aggression and concentration positively. On the basis of this results, we can conclude that Art therapy have an positive effect on the alleviation of ADHD children\'s aggression and on the change of their concentration.