This paper report the pitting corrosion behavior and grains evolution of shot peened 304 type stainless steel. The Polarization tests in 3.5%wt NaCl conducted to reveal corrosion behaviors of the samples. The measurements carried at room temperature with Ag/AgCl/KCl and Pt as reference electrode and counter electrode, respectively. The optical microscope employed to characterize the grain evolution of the sample due to shot peening processes. The transformation of pitting corrosion behavior and grain evolution was observed. The pitting corrosion is dependent upon grain evolution due to shot peening processes. The pitting corrosion resistance increase in smaller grain due to shot peening processes, although the corrosion potential shifted to less noble and passive current increased.