Abstract: A method of applying a protective layer forming material, wherein when a roller is rolled against a curved portion of a vehicle to apply the protective layer forming material, the roller is rolled at a speed that is lower than a speed when the protective layer forming material is applied by rolling the roller over a generally flat portion of the vehicle. When the roller is rolled against a portion of the vehicle having recessed and projected grooves, in order to apply the protective layer forming material, an axis of the roller is positioned generally horizontal to an extending direction of the grooves and the roller moves in a direction generally perpendicular to the extending direction of the grooves, while the roller is rolled at a speed that is lower than a speed when the protective layer forming material is applied over the generally flat portion.