A method for forming a surface layer, the purpose thereof is to form a high erosion resistant film. The method for forming a surface layer includes: arranging a member (2) in a machining fluid (3); and forming the surface layer including silicon by spacing a silicon electrode (1) from the member (2) at a predetermined distance, and by supplying silicon component from the silicon electrode (1) to the member side by applying a predetermined voltage and generating electric discharge, and an iron-based metal texture including silicon of 3 to 11 wt % is formed at a thickness of 5 to 10 μm at a portion to be treated by repetitively generating a electric discharge pulse in which a time integration value of a current value of the electric discharge pulse is in a range of 30 A·μs to 80 A·μs.