The purpose of this study was to investigate the effects of group music therapy on the emotional stabilisation and Self-Efficacy of juvenile delinquents. The subjects, who were from age 15 to 19 as juvenile delinquents, received juvenile protection Order one (1) and three (3) or Order (4) and were placed in custody designated by the Gwang Ju Family Court. The 24 subjects were divided into the experimental group (N=12), and the control group (N=12) at random. The experimental group was given 14 group music therapy session for 90 minutes each, two times a week, and the control group was not given any. Emotional stabilisation and the Self-Efficacy scores for each adolescent was compared before and after the experiment. Statistical methods used for data analysis were mean, the standard deviation, and the ANCOVA. Results are as follows. The experimental group was significantly increased in emotional stabilisation compared with the control group. The experimental group was significantly decreased in aggressive behavior compared and in stress compared with the control group. The experimental group was significantly increased in self-efficacy compared, in self-confidence compared and in self control efficacy compared with the control group. These results suggest that group music therapy are positive effects on improving the emotional stabilisation and the Self-Efficacy of juvenile delinquents.