The purpose of this paper is to clarify the demand and market power of green tea beverage brands in Japan. We use the Berry, Levinsohn and Pakes (BLP) model for analysis and focus on the effect of catechin, the functional ingredient of green tea beverages, on the demand structure and market power.The main results of the analysis are as follows: First, the consumer selects the brand with a low price if the catechin content is constant and the brand with a high catechin content if the price is constant.Second, regarding unobserved characteristics, a brand approved as food for specific health uses provides relatively high utility to consumers. Third, the market power of ITO EN, SUNTORY, Coca-Cola, KIRIN, and AEON is roughly the same; however, that of KAO is relatively low. Fourth, the trend