PURPOSE: To improve the dispersibility and stability of an inorg. particle and to enhance the adaptability thereof in various hydrophobicity utilizing fields by coating the surface of the inorg. particle with organosilicic acid represented by a specific general formula to form a modified inorg. particle.

CONSTITUTION: An water-soluble alkali salt of organosilicic acid represented by formula RSiO1.5-n/2(OH)n (wherein n is 0≤n≤1 and R is a 1-4C alkyl group, a 2-4C alkenyl group or a phenyl group) is subjected to cation exchange to prepare an active organosilicic acid solution substantially containing no alkali component. Subsequently, this active organosilicic acid solution and an inorg. particle are mixed under a condition of pH-11 to obtain a modified inorg. particle coated with the organosilicic acid represented by the aforementioned formula. As the inorg. particle, substantially spherical silica is preferable.