The dielectric-forming composition according to the invention is characterized by consisting of: composite particles for dielectrics in which part or all of the surfaces of inorganic particles with permittivity of 30 or greater are coated with a conductive metal or a compound thereof, or a conductive organic compound or a conductive inorganic material; and (B) a resin component constituted of at least one of a polymerizable compound and a polymer. In addition, another dielectric-forming composition according to the invention is characterized by containing: ultrafine particle-resin composite particles composed of (J) inorganic ultrafine particles with the average particle size of 0.1 .mu.m or smaller, and (B) a resin component constituted of at least one of a polymerizable compound and a polymer, wherein part or all of the surfaces of the inorganic ultrafine particles (J) are coated with the resin component (B), and the ultrafine particle-resin composite particles contain 20% by weight or more of the inorganic ultrafine particles (J); and inorganic particles with the average particle size of 0.1 to 2 .mu.m and permittivity of 30 or greater, or inorganic composite particles in which a conductive metal or a compound thereof, or a conductive organic compound or a conductive inorganic material is deposited on the part or all of the surfaces of the inorganic particles.