PROBLEM TO BE SOLVED: To improve the corrosion resistance of a steel material by forming a metal diffusion layer containing nickel and iron on a surface of the steel material in shot peening using NiO particles.SOLUTION: A surface treatment apparatus for forming a metal diffusion layer containing nickel and iron on a surface of a steel material comprises a chamber 110 replaced with an inert gas, a support part 120 arranged in the chamber 110 to support a substrate W, an induction heating coil 130 arranged around the support part 120 to heat the substrate W, a high frequency applying part 200 supplying a high frequency current to the induction heating coil 130 to induction heat the substrate W, and a projection material injection part 141 injecting a projection material P, in which NiO particles and SKH59 material particles harder than the steel material are mixed, to the support part 120.SELECTED DRAWING: Figure 1
