To provide an evolution strategy method, in which the search sturdiness is heightened by introducing the effect of the genetic drift to improve the self adaptability of strategic parameters, and to heighten the search sturdiness by introducing the effect of the genetic drift to improve the self adaptability of strategic parameters.

An evolution strategy calculation system comprises a storage unit for storing an array of the strategic parameters which include active strategic parameters and inactive strategic parameters and at least one probabilistically working substitution operator, an array operation unit which reads a substitution operator from the storage unit, and probabilistically operates the array of the strategic parameters of each individual by the read substitution operator and the probability of each substitution operator, and a mutation unit for causing mutation, based on the strategic parameters after the operation.