PROBLEM TO BE SOLVED : To provide a method for estimating a price function, that estimates an optimum function with which the price of real estate is predicted in each divided segment by performing the market division corresponding to a complicated market structure.SOLUTION : This cost function estimating method for calculating a predicted price of a piece of real estate with a statistical analysis has a step for setting segments, in which a market structure is composed of homogeneous object data by performing a structural change test of the object data, a step for selecting a statistical model to be used to estimate the cost function from among a plurality of statistical models in each set segment, and a step for using the selected statistical model to estimate the cost function for the object data in each set segment.