The present invention concerns a method for treating the surface of a fibrous web by mechanical grinding. According to the invention, the grinding is performed at substantially dry state by removing only the higher parts of the paper surface without substantially increasing the density of the web. By reducing the roughness of the surface by a maximum of 90%, the strength properties of the web remain essentially unchanged or they are even improved. Thus, when the roughness of the surface is reduced by about 40 to 60%, the tear strength increases with more that 5% in comparison to an untreated web. Papers and boards treated by the present method can be used for printing, packaging and wrapping.