To provide a simulation system matching with users' actual conditions.

The surplus fund simulation system comprises a reference cash flow forming step B for forming individual cash flows which serve as references for yearly balances by use of a calculation formula which is predetermined by use of input fundamental conditions; a displaying step C for accumulating the yearly balances determined from the individual cash flows and displaying the balance of each year; and a correcting step D for inputting correction requirements for correcting the fundamental conditions and correcting the individual cash flows according to the input correction requirements to form new individual cash flows. By repeating the correcting step D, the individual cash flows are renewed consecutively to form individual cash flows corrected based on the correction requirements. The yearly balances are displayed in a cumulative fashion by the displaying step C.