Sazanami and Urata and Kawai (1996) measure the cost of trade protection in Japan by partial equilibrium model. They assume that the import price is fixed even if the import quantity increases. However, actually, the import price rises with increases in the import quantity. In this paper, we improve their model so that it can take the price increase into consideration. Implications of this paper and problems to be solved in the future are summarized in the last section of this paper.