PURPOSE: To improve a surface cleaning effect and to reduce the cost thereof by successively using a first mixture contg. zinc sulfate and polishing agent and a second mixture contg. hexafluorosilicate consisting of alkaline earth metals and zinc.

CONSTITUTION: The first mixture consisting of the zinc sulfate, the polishing agent and thickener is formed. This mixture is applied on the surface of a calcareous material, such as marble and is flushed away. Next, the aq. second mixture soln. consisting of the hexafluorosilicate consisting of a group composed of the alkaline earth metals and the zinc and an aliphat. org. acid of nomocarboxylic acid is prepd. The second aq. mixture soln. is applied to small blocks on the material surface after the treatment with the first mixture and thereafter, the surface is successively subjected to buffing, by which the surface treatment is executed. Since the thin insoluble film of CaSiF6 is chemically formed on the surface, the effect of improving the surface cleanliness is improved and is maintained. The cost of the cleaning is reduced for the simplification of the work.