Abstract: The invention relates to a process of the treatment of sodium silico fluoride. In the invention, sodium silico fluoride is decomposed with a relatively high concentration of an aqueous ammonium solution or an ammonia gas to produce a mixed aqueous slurry solution of ammonium fluoride containing sodium fluoride and silica gels as solid materials, the obtained mixed aqueous slurry solution is separated to the ammonium fluoride solutions containing sodium fluoride and silica gels, respectively, by means of a physical method and then sodium fluoride, silica gels and the aqueous ammonium fluoride solution are manufactured in high purity and good yield, respectively. In the other way, the mixture of sodium fluoride and silica gels are separated from said mixed aqueous slurry solution by means of the filter, washed with water and dried. The dried mixture is separated to sodium fluoride and silica gels by means of a physical method.