Effects of positive and negative feedback on students' self-evaluation were investigated. Junior high school students were administered self-esteem scale, the Guess-Who-Test (class members nominations) and rating scales on self-confidence and self-evaluation relating to group behavior items. Then, class teachers gave each student positive feedback based on the peer ratings. The main results were as follows: (1) Though on the whole positive feedback had raising effects on self-confidence and self-evaluation, it was found larger for low self-esteem students than for high self-esteem students; (2) Additional negative feedback only to high self-esteem students did not lower their self-confidence and self-evaluation but roused their willingness to improve their behavior when they were convinced of the truth of negative feedback. Based on the above results, effects of positive and negative feedback on students' self-evaluation were discussed.