The purpose of this paper is to investigate the structure of cost-sharing for oriental medical services in the national health insurance. Out-of-pocket payment in ambulatory oriental medical care is a co-payment of KRW3,000 up to total expenses of KRW15,000, and co-insurance rate of 30% thereafetr. The empirical analysis based on medial claims data shows that the frequency of medical claims for outpatient care are mostly concentrated just below a total expenses of KRW15,000, and it decreases beyond a total expense of KRW15,000, while it rebounds between KRW17,000${sim}$20,000. This means the current co-payment(KRW3,000) in oriental medical services should be applied up to a total payment of KRW17,000${sim}$20,000, or the level of co-payment should be adjusted upward to KRW45,000 in order to be consistent in cost-sharing, between co-payment and co-insurance.