To provide a cationic resin-modified silica-dispersed liquid having a silica concentration of ≥22 wt.% and also having high transparency and excellent preservation stability by using wet silica as a raw material and to provide its manufacturing method.

In the method for manufacturing the cationic resin-modified silica-dispersed liquid having an average particle size of ≤300 nm, a silica slurry obtained by adding a wet silica having 170-230 m2/g BET specific surface area to a polar solvent so that the silica concentration may be ≥22 wt.% is atomized by a wet medium type pulverizer using a ceramic bead having the average particle size of less than 0.2 mm as a medium so that the average particle size of the wet silica particles may be ≤1 μm, then the slurry is mixed with a cyclic ammonium salt type cationic resin having an average molecular weight of less than 50,000 and also a colloid equivalent value of ≥4.0 meq/g, and the mixture is subjected to dispersion treatment by a high pressure homogenizer.