This study is to find out the effects of the art therapy on reducing the impulsiveness of ADHD tendency children. For the study, an elementary school 2nd grade boy took part in the art therapy once a week per 40 minutes, 18 times in total, from September 6, 2013 to February 28, 2014. To verify the study effects, the Korea ADHD diagnostic scale and the house-tree-person drawing test were carried out before and after the art therapy program and the two were compared. According to the results, the K-ADHDDS shows 9T points on the impulsiveness level in comparison with the former 14T points, which is a decrease of 5T points. And the HTP drawings changed to adequate size drawings showing decreases of the impulsiveness from former big size and scribbled drawings. Therefore, the art therapy proved to be an effective intervention for reducing the impulsiveness of ADHD tendency children. Since this study is single case, there are limits to make the effects generalized.