A silica sol which has excellent moisture absorption resistance and stability as well as high purity and which does not cause coloring of a solvent or a resin to which the silica sol has been applied. The silica sol contains high-purity silica particles, water and/or a liquid organic medium serving as a dispersion medium, and an organic base compound, the silica particles being dispersed in the dispersion medium, wherein the silica particles satisfy the following requirements (a) to (c): (a) the silica particles have a specific surface area, as determined through a nitrogen absorption method, of 20 to 500 m2/g; (b) the silica particles have a moisture absorption amount per specific surface area thereof of 0.5 mg/m2 or less; and (c) the organic base compound is not substantially contained in the inside thereof.