Recently, the steel parts used at the aerospace and automobile industries are required to be used high stress more than ever before in need of the weight down. Therefore, used material steel have to be a high stress, which is an indispensable condition in this field. At the consideration of parts design, high hardness of the lightweight parts has an benefit of saving fuel and material. In this study, the surface conditions are measured to know the influence on fatigue properties by shot peening. In this study, the optimum shot peening condition is investigated. Fatigue test was accomplished to investigate the effects of compressive residual stress by shot peening on fatigue characteristics. Test results show the fatigue characteristics were increased by optimum peening condition. But the fatigue characteristics were decreased by under peening or over peening condition.