PURPOSE: To prevent the self discharge of charged liq. droplets and to enhance the classification efficiency by electrostatically injecting a mixture of a nonvolatile liq. having high surface tension and the particles to be classified, and electrostatically classifying the charged dispersed liq. droplets covering the particles.

CONSTITUTION: The particles 2 and the liq. 3 are mixed in a tank 1. The mixture is passed through an electrically conductive thin pipe 4, charged, atomized by the electrostatic action of a ring high-voltage electrode 5, dispersed, and dropped. At this time, a spherical liq. droplet 10 having a thin layer of the liq. 3 around the particle 2 is formed by the surface tension of the liq. The droplets are transported by the electric-field curtain 11 of an electrostatic classifier, and successively collected by a collecting electrode 12 impressed with an AC high voltage as shown by the central marks. The particles are respectively charged with the load corresponding to their diameter, coarse particles are collected on the upstream side, and classification is accurately carried out.