According to one embodiment, a pattern formation method includes steps of forming a layer to be processed on a substrate, forming a metal microparticle layer by coating the layer to be processed with a metal microparticle coating solution containing metal microparticles and a solvent, reducing a protective group amount around the metal microparticles by first etching, forming a protective layer by exposing the substrate to a gas containing C and F and adsorbing the gas around the metal microparticles to obtain a projection pattern, and transferring the projection pattern to the layer to be processed by second etching.