PROBLEM TO BE SOLVED : To provide an information processing system for deriving an index which can contribute to objective determination of a real estate value.SOLUTION : An information processing system 1 includes an attached real estate detection part AT1 for detecting real estates to be attached in a predetermined section, and an index derivation part IX for deriving an index about marketability of real estates in the section on the basis of the number of real estates of at least two among the number of real estates to be attached, the number of real estates to be attached and subjected to the transfer of ownership due to an arbitrarily established transaction, and the number of real estates to be attached and subjected to the transfer of ownership due to auction.SELECTED DRAWING : Figure 1COPYRIGHT : (C)2017, JPO&INPIT