An inverse analysis using the optimization technique with a boundary element method is presented for quantitatively estimating residual stresses caused by volume changes in a semi-elliptical region in a structural component. In the present paper, this inverse problem is reduced to the problem of minimizing the optimization function defined as the sum of the square of differences between experimental values and numerical solutions, where experimental data include deformation at the free surface of the block with rectangular cross section subjected to surface treatment, and numerical values are calculated by using the boundary element method. In order to investigate the influence of measurement errors included in the given additional information on identification results, numerical simulation is carried out for the case where the given displacement information includes probabilistic errors with the normal distribution. Furthermore, the distributions of residual stresses measured by the X-ray diffraction technique for partially quenched S45C steel are compared with the results calculated by inverse analysis, and discussed as to the validity of the identification procedure.