The purpose of this study was to investigate the mediating effect of music therapists' self-efficacy on relationship between their professionalism and psychological burnout, ultimately finding how to prevent and cope with such exhaustion. For the purpose, the study made an online questionnaire survey of music therapists as its participants in terms of professionalism, self-efficacy and psychological burnout from April 15 to June 15, 2022. Each of the participants already had a clinical music expert's license issued by the Korea Music Therapy Association. Of total distributed copies of the questionnaire, 130 were finally collected as data. Through processing the data, this study calculated mean, standard deviation, skewness and kurtosis values. And then, the research conducted correlation analysis and regression analysis. Furthermore, this study carried out the Sobel test to examine the effect of mediation. The findings of the study can be summarized in the following. First, professionalism, self-efficacy and psychological burnout of music therapists surveyed here were correlated with one another. And second, relationship between the participants' professionalism and psychological burnout was partially mediated by their self-efficacy. In other words, the surveyed therapists' professionalism had a direct impact on their psychological burnout and, at the same time, indirectly affected the burnout via their self-efficacy.