PURPOSE : An online real estate business system and a method thereof are provided to improve the transaction success rate by renewing the price and offering interested sales information. CONSTITUTION : A sale information processing unit(301) processes investigation, registration, and deletion for sale-information. A filtering processing unit(302) processes the registration of sale-information. A reliability processing unit(303) renews the reliability of the registered sale-information. A bargaining processing unit(304) processes the online bargaining of the cost and trade condition between supplier and consumer in real-time. A transaction condition processing unit(305) processes the probability information of the deal possibility based on between processing result data of the negotiation processing unit and supplier and consumer based on the bidding price.