This study was carried out to know the effects that horticultural therapy on the improvement of the self-concept of underachiever child. The study was performed on six underachiever child of the general classes of P elementary school located in Daegu Metropolitan City. The experiment was conducted twice a week, from September 19 to December 16, 2003, total in 22 times. The examination on self-concept before and after the execution of horticultural therapy was utilized by dividing general self-concept from self-concept on learning for each lower-level area. The program also evaluated the degree of emotional and sociable developments by horticultural therapy evaluation chart(KHY type) and performed comprehensive evaluation through direct observation by horticultural therapists and the class teachers. The evaluation results on self-concept for all subject students showed meaningful difference after horticultural therapy. This is thought to promote learning motive and learning desire through various horticultural therapy programs using plants. It has shown on the change of attitude for solving problems. As explained above, it has shown that the horticultural therapy had positive effects on the formation of self-concept for underachiever child.