This paper Estimated by using The Benefit unpaid by Insurer that The privately insured used medical care service in 2006. The Korean government in June 2006 instigated an prohibition policy for Private health insurance coverage of the medical expenditure. This paper analyse how this policy affected the utilization of medical care to privately insured in the Korea. A total of 70,600 person`s claim record from private health Insurer by Random sampling were analyzed by Multiple linear regression. The changes of medical utilization were compared Price Elasticity of The Demand for Medical Care Service as dependent variables with independent variables which Co-payment including The Benefits unpaid by insurer. The principal finding is an estimated Co-payment`s elasticity of -0.006(Outpatient) and -0.008(Inpatient). The medical utilization was hardly affected by Co-payment`s changes. The highest price sensitivity is found for Outpatient`s Benefit unpaid by insurer (-1.39). Both Outpatients and Inpatients are hardly sensitive to change of Co-payment. But they have a strong reaction to change of the Benefit unpaid by insurer.