Objective: The present study aimed to examine the role that caregiver burden plays in the familial functioning, social support, and quality of family life (QOFL) of caregivers of elderly family members with dementia. Methods: A survey was conducted with 200 primary caregivers of elderly dementia patients who resided in prefecture “S”. The questionnaire consisted of items that required demographic information, the Japanese versions of the Zarit Burden Inventory (ZBI) and the Family Adaptability and Cohesion Evaluation Scales (FACES II), and scales that measure quality of family life and social support. On the basis of the median ZBI score (i.e., 30.8), participants were divided into two groups: group A (i.e., ZBI score < 30) and group B (i.e., ZBI score > 30). Stepwise multiple regression analysis was conducted with QOFL as the dependent variable. Version 24 of the Statistical Package for the Social Sciences for Windows was used to conduct all the statistical analyses; the statistical significance level was specified as 0.05. Results: Group A and B obtained average ZBI scores of 18.5 and 43.8, respectively. The study targeted 81 patients from group A (average age = 61.0 years) and 77 patients from group B (average age = 61.7 years). Time that was spent on caregiving tasks was significantly higher for group B, when compared to group A. In addition, significant differences in cohesion and adaptability, which are two dimensions that are measured by the FACES II, and QOFL emerged between the two groups. The results of the multiple regression analysis showed that cohesion (β = 0.38), practical support (β = 0.32), adaptability (β = 0.30), and living arrangement (β = −0.12) significantly predicted QOFL. Conclusion: Family cohesion and adaptability are indicators of healthy familial functioning. In order to improve the QOFL of caregivers of elderly dementia patients, it is necessary to strengthen emotional ties, maintain emotional attachment, and flexibly respond to the burden of nursing care and changes in power structures and role relationships.