In order to improve the fatigue strength of various metal materials, we have developed a surface treatment called cutting and rubbing process. In this report, the test material is high-strength ductile cast iron. Although this is a high-strength material, it has many defects that can cause cracks in fatigue tests. Fatigue tests were carried out at room temperature using a rotating bending fatigue machine operating at 50 Hz. The fatigue life of the cutting and rubbing processed specimen was much longer than that of non-surface treated specimens. Regarding the fatigue strength at 10⁷ cycles, no enhancement due to the present surface processing was attained, because of the fish-eye fracture. The fracture was caused by cracks from defects beneath the processed layer. The compressive residual stresses of the cutting and rubbing processed specimen surface measured by X-ray diffraction was 441MPa. The stress constant used in this measurement was -340 MPa / degree.