To provide a building support system and its method by which house builders can reduce costs of building expenses and increase orders received, and a customer can effectively select a house builder complying with the customer's desire from provided information to request house building.

A server device 2 installed on an intermediary trader interested side and each terminal device installed on the house builders side are connected through a telecommunication line 6. The server device 2 includes a transmission/ reception part 12 that transmits a desirable contract amount offered by the customer in advance and the information on the lowest bid price in the present bid prices offered by the house builders to a terminal device 4, and receives the bid prices transmitted from the terminal device 4 through the, telecommunication line 6, compares the bid prices received by the transmission/reception part 12 with the desirable contract amount, and extracts only the bid prices lower than the desirable contract amount to store. The lowest bid price in the stored bid prices is retrieved and sent to the transmission/reception part 12.