PROBLEM TO BE SOLVED : To provide a time series risk management system of real estate for successively evaluating the variance of rent income.SOLUTION : The initial value of the correlation coefficient of rent fluctuation between tenants and the volatility of the rent of each tenant are set, and the volatility of the rent income of overall real estate is calculated. Then, a time series data file related to a rent is added and updated per month. Each time the data file is updated, the correlation coefficient between tenants related to the rent fluctuation is recalculated, and the volatility of the overall rent income is updated by using the updated correlation coefficient. The probability distribution of a profit price is calculated by using the rent and a vacant room rate as probability variables on the basis of the updated conditions, and a risk management index is calculated on the basis of the probability distribution of the profit price.