Surface treatment method and surface treatment composition

The present invention provides: a surface treatment method by which a coating film excellent in terms of appearance improvement and durability can be formed on a coated surface at one time by easy application, irrespective of worker's ability; and a surface treatment composition suitable for use in the method. The surface treatment method of the present invention comprises applying a surface treatment composition with a polisher, the surface treatment composition comprising (A) a polymeric organic silane having a reactive group, (B) a reaction catalyst, and (C) abrasive particles comprising an inorganic compound having an average primary-particle diameter of 0.1-10,000 nm.