A method for processing a substrate includes: (a) exposing a substrate with a pattern formed on a surface thereof to a first reactive species in a chamber, thereby adsorbing the first reactive species onto the surface of the substrate; (b) exposing the substrate to plasma formed by a second reactive species in the chamber, thereby forming a film on the surface of the substrate; and (c) repeating a processing including (a) and (b) two or more times while changing a residence amount of the first reactive species at a time of starting (b).