Laser peening is an innovative surface enhancement technology to introduce a compressive residual stress on metallic materials. In this paper, residual stress, Vickers hardness and surface profile of four grades of structural steel were examined to clarify the applicability of laser peening. The results obtained are summarized as follows. 1) Laser peening conditions, which can generate large and deep compressive residual stress, were established for 400 to 780MPa grade steels. 2) Compressive residual stress becomes deeper with the increase of material strength, whereas the hardened layer becomes shallower in the same laser peening conditions. 3) The surface got dented by 10 to 30μm from the initial surface and the surface roughness (Ra) became 3.5 to 13μm after laser peening.
