This paper describes the influence of shot peening on of the peened surface and fatigue strength. Shot peening was performed by a wet blasting machine with a wide nozzle. At first, influences of particle size and geometry on characteristic values such as surface roughness, residual stress, FWHM, and Vickers hardness were examined, and then fatigue strength was studied on the peened materials. The material is a medium carbon steel (C:0.45%, 180HV) and the peening particles are alumina and glass beads. The following results are shown in this paper: (1) On the specimen a width of 83% of the wide nozzle is peened uniformly judging from chatterings of FWHM, compressive residual stresses and surface roughness. (2) Surface roughness, compression residual stress, FWHM and the maximum hardness increase with increasing particle size except for the case of 57μm particles; the maximum values are 0.52μm, 390MPa, 2.15deg, 205.6HV respectively. (3) Fatigue strength is improved using alumina and glass beads by 20% and 15%. (4) The peening process using a wide nozzle can effectively improve fatigue strength.