The authors have developed five kinds of techniques on electrostatic classification of particle size utilizing the balance of the electrostatic and gravitational force. The first is an inclined plate conveyer system. A plate conveyer consisted of parallel electrodes was constructed and four-phase traveling field was applied to the electrodes to transport particles on the conveyer. Particles were classified with size under the voltage application of appropriate frequency based on the feature that small particles were transported upward against the gravity but large particles were apt to fall down. The second technique was an inclined tube conveyer system. The principle is common with that of the inclined plate system. The third technique utilizes a circular electrostatic conveyer similar with the mass spectroscopy. The forth is also circular but utilizes the feature that a locus of the small particle is high compared to that of the large particle. The last is the combination of the linear conveyer and an electrostatic separation roller located at the end of the conveyer. Small particles were attached onto the roller charged by a charger roller. These techniques are expected to be utilized to the classification of toner and carrier particles used in electrophotography.