The purpose of this study was to investigate the effects of positive behavior support(PBS) intervention using Picture
Exchange Communication System(PECS) on problem behaviors of the elementary school student with autism
spectrum disorder. For the study, a child with autism spectrum disorder was selected and individualized PBS with
functional assessment were implemented using multiple treatment design. PECS intervention was conducted with
setting events and antecedent events, alternative behaviors, consequences. The baseline and intervention were
observed in a special class room during study and break time. Remaining effects were observed two weeks after
last intervention. Social validity were measured by 50 people, who work as a special education teacher or special
education students at university. The results of this study is as follows. First, the effect of PBS intervention using
PECS makes strong decrease of acquisition function behavior and little decrease of evasion function behavior.
Second, the effect of PBS intervention using PECS was maintained even after intervention ended. Third, social
validity of this research was over average level, makes chance to apply this intervention on public education. The
significance of this study is as follows. First, PBS intervention using PECS can be applied reducing problem
behavior of an non-verbal elementary school student with severe autism used as a kind of communications. Second,
PBS intervention using PECS made significant differences between effective and less effective intervention applied at
an elementary school student with autism spectrum disorder who have problem at sensory stimulus.