A method for selectively modifying a base material surface, includes applying a composition on a surface of a base material to form a coating film. The coating film is heated. The base material includes a surface layer which includes a first region including silicon. The composition includes a first polymer and a solvent. The first polymer includes at an end of a main chain or a side chain thereof, a group including a first functional group capable of forming a bond with the silicon. The first region preferably contains a silicon oxide, a silicon nitride, or a silicon oxynitride. The base material preferably further includes a second region that is other than the first region and that contains a metal; and the method preferably further includes, after the heating, removing with a rinse agent a portion formed on the second region, of the coating film.