The purpose of this study is to develop and validate a music therapist’s professionalism scale that can measure the level of professionalism of music therapists. The procedures and results are as follows. After analyzing previous studies and literature, 10 music therapists were interviewed in-depth, and 113 initial items were developed by deriving concepts and factors for the professionalism of music therapists. After that, four factors and 36 preliminary items questions were derived through content validity verification, a review form a scholar of Korean Literature and face validity verification. A preliminary survey was conducted on music therapists to collect 330 copies of data, and four factors and 23 main survey items were derived through item analysis and exploratory factor analysis. After collecting 378 copies of data from music therapists under the same conditions as the preliminary survey, the final scale of 4 factors and 23 items were completed through item analysis and confirmatory factor analysis. The four factors were ‘professional knowledge and skills’, ‘work attitude’, ‘work philosophy’, and ‘professional engagement’. In addition, evidence of accredited validity and convergence validity was secured through external criteria. The scale developed as a result of this study is significant in that it can present specific empirical data on the professionalism of domestic music therapy, reflect the unique characteristics of music therapy with different characteristics from other professions, contribute to the activation of empirical study, and can be used in education and research fields of music therapists