The purpose of this study is to identify the factors affecting job burnout by analyzing the job burnout patterns and levels in teacher librarians and to empirically investigate the relationship among the effective factors. For qualitative research 17 teacher librarians were intentionally chosen and in-depth interview was conducted from September 5, 2018 to October 30, 2018. The in-depth interview shows that the factors affecting the job burnout of teacher librarians are the sense of belonging, professional identity, professional development opportunities, reputation of teacher librarians, social support and job engagement which defined as librarians’ job specificity. For the reliability and validity of the measurement tools, six teacher librarians were primarily investigated from December 5, 2018 to December 7. After that a survey was carried out through the web questionnaire for two weeks from December 20, 2018 to January 3, 2019. A total of 305 copies were collected, all of which were used for the analysis. The results of the quantitative study are summarized as follows. First, concerning the job specificity of teacher librarians, the factors affecting job burnout were professional identity, reputation of teacher librarians, and social support. Second, concerning the job specificity of teacher librarians, the factors affecting job engagement were sense of belonging, professional identity, and social support. Third, as a result of verifying the mediating effect of job engagement in relation to job specificity and job burnout of teacher librarians, professional identity showed complete mediating effect and social support showed partial mediation effect.