According to various embodiments of the present invention, a device for mediating a real estate for sale comprises : a first device for transmitting information on a real estate for sale; a second device for inquiring registered real estate information; and a processor coupled to the first and second devices. The mediating device generates and registers real estate information including lease identifier information of a real estate for sale in information of a transmitted real estate for sale when registration for a real estate for sale is requested by the first device, and generates real estate information including a lease identifier representing leasable or under-lease information of each real estate for sale of the registered real estates for sale when searching for the real estates for sales is requested by the second device. The second device can display the real estate information including the lease identifier of the real estates for sale in a display unit.(311) Member joining(313) Member joining information registration(321) Real estate information?(323) Receive required information and/or additional information(325) Register a real estate(331) Change real estate information(333) Change real estate information(341) Real estate inquiry?(343) Real estate information display, Leasable/under-lease display(345) Execute a corresponding function(AA) StartCOPYRIGHT KIPO 2018