To provide a system capable of preventing a real estate property marked by a user from being left without being monitored.

This transaction support system for the real estate property inquires property information of each room number in multiple dwelling houses from a server 4 via a communication network 3, in response to a request from a client device 2 of the user, and the server 4 is provided with: a web page generation and storage part 5 for generating and storing an web page for displaying a business negotiation situation of each room number and the registered room number in every user, and for promoting a new registration or a change of a desired room number, in every user; a property information database 91 for storing the business negotiation situation of each room number; a reflecting part 7 for reflecting updated information on the web page stored in the web page generation and storage part, when the property information database is updated; and a web distribution part 6 for extracting the corresponding web page from the web page generation and storage part, in response to the user request, to be distributed to the client device.