The Government has recently planned to improve the medical insurance drug price systems by removing the drug margin occurring from the difference between the official and purchasing prices, and instead by setting prices through adding drug administration casts calculated to the purchasing costs. In the circumstances, the major policy and implementing issues are how to define the drug administrance cost and how to calculate them. This study attempts to provide for the conceptional and operational definitions and thereby develop a costing model for the cost. The relationship between the current systems of medical services costs and prices were reviewed to define the concept of the costs. The study defined the costs from the narrow and wide prospective of meaning, and three operational definitions were provided. The costing model was developed applying the departmental costing principles. Finally, several prerequisites that have to be considered for the implementation of the definition and the model from the practical viewpoint.