To study the effect of shaping on on-task behavior and task accuracy of 7 to 10 year-old pupils with attention deficit/hyperactivity disorder. The subjects were six pupils from Yuwaprasartwaithayopathum were tested by disruptive behavior rating scale-teacher/parent form (DBRS) to identify that they were attention-deficit/hyperactivity disorder, predominantly inattentive type (ADHD-I) and attention-deficit/hyperactivity disorder, combined type (ADHD-C). The subjects were divided into two groups, the control group and the experimental group. The experimental group was taught by shaping method. After that both groups were given the task to evaluate the task performance on both on-task and task accuracy. The results were as follows; the experimental group who were taught by shaping method showed significantly better score on on-task behavior and task accuracy than the control group. (p<.05).