A die modification estimate system comprises a first unit which acquires contents of modification of a die specified by using an input unit. A second unit reads respective reference values for cost estimation, according to the specified contents of the die modification, from a storage unit. A third unit reads respective estimate functions of cost items according to the specified contents of the die modification, from the storage unit. A fourth unit calculates an estimated cost of each of the cost items based on a corresponding one of the reference values and a corresponding one of the estimate functions. A fifth unit stores the estimated costs in the storage unit. A sixth unit calculates a total amount of the estimated costs read from the storage unit. A seventh unit outputs the total amount of the estimated costs to an output unit.