This study aims to find out the determinants of burnout in order to better understand the burnout process among social workers. For this purpose, a hypothetical model which explains the relationships among 8 job-related stressors (role ambiguity, role overload, difficulties in solving problems of clients, conflict with the clients, lack of support from the supervisor, closed communication pattern, bureaucracy, and lack of accountability), 4 mediators (job-stress, professional role performance, abiding by the agency policy and partiality in service delivery), and 4 dimensions of burnout (physical exhaustion, psychological exhaustion, depersonalization and personal accomplishment) was developed. Using the data collected from 207 social workers, the hypothetical model was tested. For data analysis, a path analysis was used, and the best-fitting model was found(df=66, $x^2$=63.250, GFI=0.962, CFI=1.00). As a result of this study, the following results were found. Burnout among social workers was increased by the 6 job-related stressors(role ambiguity, role overload, difficulties in solving problems of clients, conflict with the clients, lack of support from the supervisor, closed communication pattern). Job-stress, the mediating variable of the emotional path to burnout, increased professional role performance and the abiding by agency policy, and finally increased burnout. On the other hand, professional self-efficacy (which consists of professional role performance, abiding by agency policy and partiality in service delivery), the mediationg variable of the cognitive path to burnout, reduced burnout when the professional role performance was high, and abiding by agency policy and partiality in service delivery were low.