The present invention provides a sol of spinous inorganic oxide particles not containing coarse particles, in which particles having extremely homogeneous particles are dispersed in a solvent. An acidic silicic acid is added to a dispersion liquid of core particles to grow core particles, and then again the acidic silicic acid is added at the addition rate 1.2 to 1.8 higher than that in the previous step to prepare a sol of spinous inorganic oxide particles. Then the sol is subjected to centrifugation to remove coarse particles having the diameter of 800 nm or more, thus spinous inorganic oxide particles having peculiar form such as a spinous one being obtained.取得不含有粗大粒徑，粒徑極為均勻之微粒子於溶劑中分散而成的金平糖狀無機氧化物溶膠。於核粒子分散液中添加酸性矽酸液令核粒子成長後，以前述添加速度之1.2~1.8倍的添加速度再度添加酸性矽酸液令該核粒子成長，調製金平糖狀無機氧化物溶膠，其次，將該溶膠予以離心處理除去粒徑800nm以上的粗大粒子，取得作成所謂金平糖狀之特異形狀之微小球狀的無機氧化物微粒子。
