PROBLEM TO BE SOLVED : To save the manpower of the calculation of a bad loan reserve amount considered to be required in a financial institution and to perform simulations by changing parameters used for the calculation. SOLUTION : A real estate security loan reserve amount calculation system is provided with a data fetching device 12 fetching data regarding a loan balance for each debtor and the data regarding the appraised amount of real estate security, and a central processing unit 11 calculating a reception maximum amount recoverable from the security on the basis of the data regarding the security appraised amount fetched in the data fetching device 12, calculating security shortage on the basis of the reception maximum amount and the loan balance fetched in the data fetching device 12, calculating a reserve amount for each debtor from the security shortage and a reserve rate read from a storage device 18 and calculating the increase/decrease of the reserve amount at the time of changing the parameters used for the calculation.