This study tries to investigate inequity in supplementary private health insurance insured in terms of the analysis of insurance insured general characteristics and to analyze the influence of supplementary private health insurance on their admission and their outpatient medical utilization behavior. As a result of the analysis of the general characteristics of supplementary private health insurances insured, it has turned out that men, persons at low ages, people with a spouse and chronic diseases, and persons with a high income have applied such insurances more. We can also tell that low-income classes have difficulty in applying private health insurances as people in the fifth income quintile have applied such insurances about 9 times as much as those in the first income quintile. The analysis of supplementary private health insurance insured health care utilization behavior has revealed that both male and female insured aged less than 55 and without chronic diseases have increases the number of their use of health care, their patient charge, and their medical cost per visit.