PROBLEM TO BE SOLVED : To obtain the fluctuation of real evaluation of a target real estate from an REIT securities price on the real time basis.SOLUTION : The total market value of real estate securities of a brand is determined from the market value of REIT (J-REIT) real estate securities of of the brand, and the underlier price of the brand is calculated by inversely using a known Black-Scholes equation or the like. The evaluation index of the target real estate of the brand is created through a profitability rate to this underlier price, and the fluctuation of the index is taken as a real-time index 5, whereby the fluctuation of evaluation of the real estate can be known timely from the market value of the real estate securities on the real time basis.