PROBLEM TO BE SOLVED : To support investment judgment such as the structural analysis of a price difference or an investment return difference generated due to the personal attributes of real estate property and the analysis of a price (including a rental fee) fluctuation risk.SOLUTION : Advertisement information related with real estate is collected, and when it is judged that the transaction of property which is previously advertised and not this time is concluded, a condition indicated by the previous advertisement information is adopted as the information when the transaction is concluded so that the transaction conclusion information can be stored. Then, a function expression including a relation between the price of the real estate property and the condition of the real estate property is derived from the stored transaction conclusion information. This function expression is obtained as a logarithmic function indicating a relation between the logarithm of each condition and the logarithm of the price. When the condition of arbitrary real estate property is inputted to the function expression, the price of the objective real estate property is estimated. Moreover, a dummy function is adopted as the variables of the function expression, and the dummy function is changed so that the change of the price against the change of the variables can be outputted so as to be recognizable.