An aqueous titanium oxide-dispersed sol comprising titanium oxide particles dispersed in water, said sol comprising chloride ions in an amount of 50 to 10,000 ppm by weight as the chlorine element. Titanium tetrachloride is hydrolyzed to form an aqueous titanium oxide-dispersed sol and the chloride ion concentration thereof is controlled. Another aqueous titanium oxide-dispersed sol comprising brookite-type titanium oxide particles dispersed in water, said titanium oxide particles having an average particle size of not more than 0.5 .mu.m and a specific surface area of not less than 20 m.sup.2/g. Addition of titanium tetrachloride to hot water at 75 to 100.degree. C. followed by hydrolysis at 75.degree. C. to the boiling point of the mixture.