A substrate processing method includes a substrate holding step of holding a substrate in a horizontal orientation by means of a substrate holding unit, a liquid film forming step of supplying a processing liquid to an upper surface of the substrate held by the substrate holding unit to form a liquid film, an upper surface covering step of discharging, above the substrate held by the substrate holding unit, an inert gas radially and parallel to the upper surface of the substrate from a center toward a peripheral edge of the substrate to form an inert gas stream flowing parallel to the upper surface of the substrate and covering the upper surface of the substrate, and a liquid film removing step of discharging an inert gas toward the upper surface of the substrate to remove the liquid film, formed by the liquid film forming step, from the upper surface of the substrate.