The impacts produced by cavitation bubble collapses can be used for surface modification to improve fatigue strength in stead of shot peeing. The cavitation impacts also improve corrosion resistance. In case of cavitation around a high-speed submerged water jet, i.e., a cavitating jet, the cavitating region and cavitation intensity can be controlled by hydraulic parameters such as upstream- and downstream-pressure of a nozzle. It can be said that a cavitating jet is very useful for practical application. In the present paper, examples of the surface modification such as the improvement of the fatigue strength and corrosion resistance by using a cavitating jet were shown, including the explanation of a cavitating jet flow.