The skin effect caused by high-power electric pulses can be used for modification of the surface microstructure in metallic materials. The electric current pulses of high amplitude and short rapid surface heating followed by melting and rapid solidification due to heat exchange with the bulk. New high-current multi-pulse equipment was engineered and used for the surface modification of a stainless steel. The microstructure was investigated by transmission electron microscopy as a function of the distance from the surface. Rapid surface heating and high cooling rate caused drastic changes in the initial austenitic structure, amorphization of the surface layer and pronounced mechanical twinning in the subsurface region.