Disclosed is a method for producing silica-zirconia composite oxide particles each coated with a silica layer, which is characterized in that a liquid dispersion of silica-zirconia composite oxide particles is obtained by reacting an alkoxide of silicon and/or a condensable compound derived from the alkoxide with an alkoxide of zirconium and/or a condensable compound derived from the alkoxide in a water-containing solvent that contains acetonitrile so that the reaction liquid is to contain not less than 10% by mass of acetonitrile, and then the surface of each silica-zirconia composite oxide particle is coated with a silica layer by reacting the silica-zirconia composite oxide particles dispersed in the liquid dispersion with an alkoxide of silicon and/or a condensable compound derived from the alkoxide in the liquid dispersion of silica-zirconia composite oxide particles.
