PURPOSE: To eliminate surface pitting due to air bubble marks, to obtain a smooth finish surface having gloss by the transfer of a film and to enhance durability, by arranging a specific hydrophobic film in a retaining mold before casting concrete in said retaining mold.

CONSTITUTION: A hydrophobic sheet 2 having a microvoid whose max. pore size is 0.1W200μm and air permeability of 500 sec/100 cc or less is arranged to the inner surface of a retaining mold and concrete is cast in said retaining mold. As the material forming the hydrophobic sheet 2, all of plastics, ceramics and a metal can be used. Especially, as the plastics, 'Teflon(R)', polyethylene, polystyrene, polyester and polyvinyl chloride are desirable. The thickness of the sheet is not especially limited but 50W100μm is pref. from the aspect of workability. By using a sheet like article satisfying all of physical properties, the generation of surface pitting or cavities due to air bubble marks is eliminated and a gloss surface is obtained.