This invention deals with a process for manufacturing high purity silica which comprises making an aqueous alkali silicate solution into fine fibrous gel in a coagulant, treating the fibrous gel obtained with an acid-containing solution, and then with water to extract and remove impurities; and optionallly heating a resulting silica at a temperature of 1,000.degree. C. or higher. Thus obtained silica is preferably used as a filler, especially, the one for resin compositions for encapsulating electronic parts; etc.