Purpose: The purpose of this study was to identify factors that influence burnout in primary family caregivers of elders with dementia. Methods: The study was conducted from June 28 to July 14, 2011 with 93 registered primary family caregivers of elders with dementia from Seoul Dementia Support Center. Each participant consented to complete a structured questionnaire of; 22 items to measure care burden (5-point), 15 items for social support (7-point), 33 items for coping (4-point) and 22 items for burnout (7-point). Results: The majority of the participants were women, mainly spouses and daughters. Average age was 68.84 and average care period, 2 years or more. The majority reported they spent 19-24 hours a day in care. Mean scores for burnout, social support, coping, and care burden were 79.44±18.13, 70.46±18.22, 93.09 ±13.07, and 51.09±17.95 respectively. Statistically significant factors were care burden and social support, which accounted for 52.8% of total variance (F=31.553, p<.001). Care burden was greater than social support in accountability. Conclusion: Burnout of primary family caregiver is influenced by characteristics of care, care burden and social support. Therefore, it is important to take these variables into account when developing nursing programs to reduce care burden and increase social support.