The present invention is to provide a method for shot peening for producing a high compressive residual stress in a gas carburized steel that has a soft layer. In this method, a depth where the maximum compressive residual stress is generated is estimated and the hardness on the surface or near the surface is not used. The depth where the maximum compressive residual stress is generated is estimated by multiplying the depth where the maximum stress is generated under contact stresses caused by the collision of shot media by the constant K. A processed steel that comprises a gas carburized steel and that has a hardness at that depth that exceeds 750HV is used. Shot media that have a hardness that is greater than that of the processed steels at that depth by 50HV or more are shot onto the processed steels to produce a high compressive residual stress in the processed steels.