After a water film is formed on a wafer front surface in a chamber, the water film is supplied sequentially with an oxidizing component of an oxidation gas, an organic acid component of an organic acid mist, an HF component of an HF gas, the organic acid mist, and the oxidizing component of the oxidation gas. As a result, the HF component and the organic acid component provide cleaning effect on the wafer surface, and a concentration of the cleaning components in the water film within a wafer surface can be even.