Catalytic metal nanoparticles can be attached on a base. A pre-treatment method for plating includes a catalytic particle-containing film forming process of forming a catalytic particle-containing film on a surface of a substrate by supplying, onto the substrate, a catalytic particle solution which is prepared by dispersing the catalytic metal nanoparticles and a dispersing agent in a solvent containing water; a first heating process of removing moisture contained at least in the catalytic particle-containing film by heating the substrate to a first temperature; and a second heating process of polymerizing the dispersing agent to have a sheet shape by heating the substrate to a second temperature higher than the first temperature after the first heating process and fixing the catalytic metal nanoparticles on a base layer by covering the catalytic metal nanoparticles with the sheet-shaped dispersing agent.