To provide a process for efficiently producing org.-inorg. composite particles which have various excellent characteristics, such as hardness, mechanical strength, elasticity and hydrophobic property, and are adequate as additive to toner, etc.

This process includes a hydrolysis stage for hydrolyzing a part or all of at least one kind of the hydrolyzable silicon compds. selected from a group consisting of the compds. expressed by the formula and their derivatives for obtaining hydrolyzate and/or its condensate in the presence of an acid, a polycondensation stage for subjecting the hydrolyzate and/or its condensate to polycondensation in the presence of a base, and a stage for bringing the radical polymerizable groups into radical polymn. reaction. In the formula, R1 is a 2 to 20C org. group contg. the radical polymerizable groups, X is a hydrolyzable group and (m) is an integer from 1 to 3. If (m) is ≥2, at least one may be 2 to 20C org. group contg. a radical polymerizable group and others may be the org. group which does not contain the radical polymerizable group.