Physical characteristics of ATO fine particles capable of exhibiting such optical properties as a high visible light transmittance, a low solar radiation transmittance, and a low haze value when the ATO fine particles are formed on a transparent substrate or in the substrate are clarified, and the ATO fine particles having the physical characteristics thereof are manufactured. The ATO fine particles having such physical characteristics that a size of a crystallite constituting the ATO fine particles is 4 to 125 nm, and that a specific surface area of the fine particles of 5 to 110 m.sup.2/g can exhibit the above-described optical properties, and an example of a method for manufacturing thereof is to parallel-drop an antimony chloride alcoholic solution and an ammonium hydrogen carbonate aqueous solution in a tin chloride aqueous solution, thoroughly wash generated precipitates, dry and calcinate them in an atmosphere, thereby the ATO fine particles are manufactured.