It is of great important to analyze the competitiveness of Korea's agricultural products at international markets in that such an analysis provides us with the knowledge on where our agricultural products are and how strong the competition is. The main factors to determine the competitiveness of a product at market is degree of differentiation that reflects the consumers' preferences. Differentiation could be considered a process that makes a product more heterogeneous to its substitutes. In general, the demand f highly differentiated products is hardly affected by the change in price of substitutes. Thus, the degree of substitution can be used as one of the indices of competitiveness. Feenstra suggested a way of measuring substitution elasticities through CES utility function. The elasticities estimated can be interpreted to indicate the competitiveness of a country at world market. Estimated elasticities can be interpreted to indicate the competitiveness of a country at world market. Estimated elasticities of substitution of Korea are much larger than those of other countries, which says that agricultural products of Korea are even less competitive at international markets. The US's elasticity of substitution was smallest among the estimates, so the US products have the strongest competitiveness at exporting market.