Purpose: The purpose of this study was to investigate the influencing factors on health-related quality of life according to body mass index (BMI) in middle age people. Methods: Using the 2017 Korea Health Panel Data, a total of 4,711 subjects age 40–64 were selected and classified into four groups based on BMI levels (underweight, normal weight, overweight, obese). Influencing factors according to BMI in middle age people was analyzed using multiple regression. Results: Activity limited was the most influential factor for health-related quality of life in middle age people. Walking and stress were factors influencing health-related quality of life in all weight groups. In the overweight and obese group, suicidal impulse was a significant influencing factor on health-related quality of life. Conclusion: To improve the health-related quality of life of middle age people, effective walking and stress management for maintaining and managing health, as well as managing suicide risk in the overweight group and obese group are required.