PURPOSE: To classify a large number of superfine particles into respective diameter ranges by utilizing the mobility of the particle by arranging an acicular electrode on the center axis of an outer tube, furnishing a tubular electrode to surround the tip of the acicular electrode and impressing a voltage between the electrodes.

CONSTITUTION: A clean gas inlet hole 3 is provided at the center of one end 1A of an outer tube 1, a hole 2 to introduce a gas contg. superfine particles is furnished around the hole 3, and plural superfine particle discharge ports 7 to 9 are concentrically arranged on the outlet end. An acicular electrode 10 having a length of 70% of that of the outer tube 1 is furnished on the center axis of the outer tube 1, and further a tubular electrode 12 is provided on the outer periphery or inner periphery of the outer tube 1 to surround the tip of the acicular electrode 10. A power source 13 is furnished to impress a voltage between both electrodes 10 and 12. Consequently, the superfine particle entrained by a gas flows in the device by the mobility corresponding to the impressed voltage, and the particles are classified into respective diameter ranges and discharged from the discharge ports 7 to 9.