This study analyzes actual conditions of private health insurance empirically by using the decision to join Korea Health Panel data. First, the study investigates how sociodemographic factors influence joining the private health insurance. Next, the relationship between the private health insurance membership and the frequency of medical service utilization is analyzed. The main results of these analyses can be summarized as follows: the socially vulnerable are less likely to join private health insurance relative to the middle and upper classes. The frequency of medical service utilization of private insurance members is relatively higher. This fact contains the possibility that the middle and upper classes are able to receive more medical services through private health insurance membership, while the socially vulnerable have difficulty with obtaining medical services in spite of much need. Therefore, policies are needed which manage the private health insurance more effectively and secure the publicity of health service socially.