A method for calculating a residual stress in a metal material, the method using an inherent strain method and comprising: preparing (S 1) a measured value of a residual stress in each of a plurality of portions on a surface of a metal material and each of a plurality of portions on a cutting face which is formed by cutting the metal material; creating a plurality of finite element models each having a shape identical to that of the metal material after the cutting, the metal material after the cutting including a part of the surface and the cutting face; setting, for each of the plurality of the finite element models created in the creating, a parameter enabling an inherent strain to be applied; deriving, for each of the plurality of the finite element models for which the parameter is set in the setting, a calculated value of the residual stress in each of the plurality of the portions on the surface and each of the plurality of the portions on the cutting face, based on finite element analysis; and calculating, for each of the plurality of the portions on the surface and each of the plurality of the portions on the cutting face, a difference between the calculated value of the residual stress derived in the deriving and the measured value of the residual stress prepared in the preparing (S 1), wherein as an optimization problem of minimizing the difference between the calculated value calculated in the calculating and the measured value, after an optimal solution of the parameter is determined by repeating the setting, the deriving, and the calculating while adjusting the parameter, a parameter value at which the optimal solution is determined is set for a finite element model having a shape identical to that of the metal material before the cutting, and a residual stress is calculated for the finite element model, based on the finite element analysis. preparing (S 1) a measured value of a residual stress in each of a plurality of portions on a surface of a metal material and each of a plurality of portions on a cutting face which is formed by cutting the metal material; creating a plurality of finite element models each having a shape identical to that of the metal material after the cutting, the metal material after the cutting including a part of the surface and the cutting face; setting, for each of the plurality of the finite element models created in the creating, a parameter enabling an inherent strain to be applied; deriving, for each of the plurality of the finite element models for which the parameter is set in the setting, a calculated value of the residual stress in each of the plurality of the portions on the surface and each of the plurality of the portions on the cutting face, based on finite element analysis; and calculating, for each of the plurality of the portions on the surface and each of the plurality of the portions on the cutting face, a difference between the calculated value of the residual stress derived in the deriving and the measured value of the residual stress prepared in the preparing (S 1), wherein as an optimization problem of minimizing the difference between the calculated value calculated in the calculating and the measured value, after an optimal solution of the parameter is determined by repeating the setting, the deriving, and the calculating while adjusting the parameter, a parameter value at which the optimal solution is determined is set for a finite element model having a shape identical to that of the metal material before the cutting, and a residual stress is calculated for the finite element model, based on the finite element analysis.