PROBLEM TO BE SOLVED : sellers purchase amount suitable for the needs of a real estate quauntity assessment device for assessing the purchase amount. SOLUTION : the desired plurality of calculating system is selected from the computing system of the estate of buying amount is calculated, and the result is displayed on a screen of a display device or the like can be confirmed by, suitable for the needs of various sellers purchase amount estate quauntity can be assessed. Selected drawing : fig. 2