To provide an organic-inorganic composite particle which has sufficient thermal conductivity, hardly causes deterioration in thermal conductivity during use, and can be produced by a simple method; a method of producing the organic-inorganic composite particle; a thermally conductive resin composition containing the organic-inorganic composite particles and a matrix resin; and a method for producing the thermally conductive resin composition.

The organic-inorganic composite particle comprises a core consisting of a vinyl polymer, inorganic particles covering the core, polyalkoxy siloxane included between the core and the inorganic particles. The thermal conductivity of the inorganic particles is 10 W/(m*K) or higher. In the method for producing the organic-inorganic composite particle, a monomer mixture comprising 100 pts.wt. of a polymerizable vinyl monomer, a polymerization initiator, and a polyalkoxy siloxane oligomer which is inert to the polymerizable vinyl monomer is subjected to water-based suspension polymerization in the presence of 0.5 pts.wt. or more of the inorganic particles with the thermal conductivity of 10 W/(m*K) or higher.