PROBLEM TO BE SOLVED : To provide a system that effectively selling information and buying information (supply information) of lots, buildings, etc., to a real estate buyer and tenant (consumer side) and can further perform operations consistently from receiving real estate selling information up to bidding.SOLUTION : This system includes an integration site for collecting and storing real estate information, members' sites connected to the integration site, and a provider display changing means for making real estate supply information include the display of a real estate itself and the display of a real estate information provider, also changing the display of the real estate provider from the display of an initial provider provided to and stored in the integration site to the display of a specific key agent determined by or related to the operating subject of the integration site and providing combined information of the display of the changed key agent and the initial display of the real estate itself to the members' terminals in providing the real estate supply information to the members' terminals in response to real estate demand information that is supplied to the integration site and transmitted from the members' terminals.