There are disclosed insulated ultrafine powder comprising electroconductive ultrafine powder which is in the form of sphere, spheroid or acicular each having a minor axis in the range of 1 to 100 nm and an insulating film applied thereto; a process for producing the same which is capable of covering the surfaces of the insulated ultrafine powder with the insulating film having a thickness in the range of 0.3 to 100 nm without causing any clearance or vacancy; and a resin composite material which uses the same. A high dielectric constant of the material is assured by adding a small amount of insulated ultrafine powder wherein an insulating film is applied to the electroconductive ultrafine powder, while maintaining the processability and moldability that are the characteristics inherent in a resin material.