A method of producing silica-based particles includes, when a dispersion liquid of composite oxide particles is prepared by simultaneously adding an aqueous silicate solution and/or an acidic silicic acid solution and an aqueous solution of an alkali-soluble inorganic compound in an alkali aqueous solution or in an alkali aqueous solution with seed particles dispersed therein, if required, the aqueous silicate solution and/or the acidic silicic acid solution and the aqueous solution of alkali-soluble inorganic compound are added so that the molar ratio of MOx/SiO2 are in a range from 0.01 to 2, herein MOx denoting an inorganic oxide other than silica and SiO2 denoting silica to prepare the dispersion liquid of composite oxide particles with an average diameter (Dp1) in a range from 3 to 300 nm.