This paper introduces a proposed neural network-based data mining method that utilizes company's internal data about customers for the purpose of marketing strategy such as target marketing and direct marketing. Unlike past data mining approaches that put market survey or customer feedback data into input values, Fuzzy ART neural network proposed in this paper takes customer's purchasing history as input values and cluster similar customers into groups. Step by step procedures of how to implement Fuzzy ART algorithm is provided, and practical considerations in order for it to be used in marketing management in the context of electronic commerce are discussed.