A method for removing inorganic foreign matters from the surface of a substrate made of silicon or glass or the surface of an inorganic coating formed on the surface of the substrate, which includes applying a light beam in a wavelength range which makes the light absorption coefficient of at least one of a material of the substrate, a material of the inorganic coating and the inorganic foreign matters be at least 0.01/cm, to the surface of the substrate or to the surface of the inorganic coating in an application amount of at least 10 J/cm2 in an oxygen- or ozone-containing atmosphere, and exposing the surface of the substrate or the surface of the inorganic coating having a negative surface potential to an acidic solution having a pH ≦6.