In Korean society, offenders with mental illness are stigmatized because their behaviors are overlaid with images of cruelty or unpredictability. The number of mentally ill offenders is increasing rapidly compared to general offenders, and their recidivism rate is high. However, most studies focused on theoretical approaches and case analysis in foreign countries. In particular, little research explores the lives of offenders with mental illness and analyzes the socio-demographic environment, treatment, and factors associated with recidivism or non-recidivism. This study analyzes various environmental backgrounds, treatment experiences, and recidivism cases after treatment completion into 1) life area, 2) turning point, and 3) adaptation through the life history research method created by Mandelbaum. Among the total court-order treatment cases, 4 cases of recidivism and non-recidivism were selected for the study. As a result, it was found that the important factors determining recidivism/non-recidivism were understanding treatment, social support system, and willingness to a better life. Based on the results of this analysis, policy and practical implications were provided for community rehabilitation and recidivism prevention among offenders with mental illness.