Durability assessment for the suspension system of the vehicle is very important. In order to secure reliability on the results of durability assessment and fatigue design criterion, accurate stresses for the interesting component must be basically calculated. In this paper, numerical stress analyses for the automobile’s coil spring were performed. Residual stresses by shot peening were also analyzed. The effects of the stress analysis results on fatigue strength of the coil spring were discussed. From the results, fatigue durability of the shot peened coil spring could be considerably improved by the effects of compressive residual stress. However, being attacked by corrosive environments, it could decrease by corrosion fatigue degradation.