Organic-inorganic composite particles include: a vinyl polymer that is a polymer of a polymerizable vinyl monomer; and inorganic particles including inorganic oxide and/or inorganic nitride. The thermal conductivity of the inorganic particles is 10 W/(m·K) or more. The inorganic particles are subjected to a surface treatment by acidic phosphoric acid ester having no polymerizable functional group, and by at least one polymerizable compound selected from the group consisting of: carboxylic acid having a polymerizable functional group; acidic phosphoric acid ester having a polymerizable functional group; and lactone having a polymerizable functional group. The polymerizable compound is bonded to the vinyl polymer, and the inorganic particles are unevenly located on surface layers of the organic-inorganic composite particles so that the inorganic particles form one or more layers.