PROBLEM TO BE SOLVED : To allow an information exchange mediating functioning as a WWW server on the Internet to contribute to significant mutual information exchange between, for example, a real estate seller and a real estate buyer, and between a real estate buyer and a housing land and building dealer.SOLUTION : A database of real estate outline information that a member seller opens allows real estate buyers and others to freely retrieve and browse data while keeping the users anonymous. A database of company outline information of the housing land and building dealer that a member land and building dealer opens allows real estate buyers and others to freely retrieve and browse data. A seller is able to sell real estate without asking the housing land and building dealer for brokerage, and hence economic effects are large. A possible real estate buyer is able to ask a land and building dealer that the buyer selects for real estate brokerage and economical effects on the seller are large.