In this paper, the relationship between a customer and a company was analyzed from a viewpoint of information technology (IT) progress and a marketing strategy. First, in the marketing, the background than to which greater importance is attached to relationship was discussed at the viewpoint of the change of a market, and the fast progress of an information technology. Next, The customer relationship type was divided into the "loyalty relation" formed based on a customer loyalty, and the "cooperative relation" formed based on cooperation by an interaction with a customer, and a construction purpose, a customer's role, and the main purposes of use of information technology were discussed. At the last, Since the practice had expanded and evolved with progress of an information technology, in order that customer relationship might build "loyalty relations" and "cooperative relation", the situation where an information technology was utilized was discussed.