This study developed the prevention education program of smartphone overuse for adolescents in middle school and testified its outcome. Finally the 4-session prevention education program for smartphone overuse was developed. 1st session was composed of psychoeducation about smartphone overuse and its side effect by quiz question. 2nd session smartphone addiction and brain change, 3rd session motivational enhancement program for smartphone overuse, 4th session cognitive behavioral program for it. The outcome was testified by internet addiction scale, smartphone addiction scale, and school adaptation scale for 2 classes of middle school students(experimental and control class). 2 Main results were as follows; First, the smartphone addiction total score and cyberworld orientation of the students participating in it were statistically significantly reduced. The difficulty of daily living and abstinence symptom due to smartphone overuse of them tended to reduce. Second, internet addiction total and all subscores of them were not changed. Third, class adaptation of them was statistically significantly increased and school adaptation total score and teacher adaptation of them tended to increase. Its meaning, implication and limitation were discussed.