PURPOSE: To attain a highly accurate classification of superfine powder by combining a cylindrical face having a plural jet nozzles penetrating radially to a coarse powder pipe concentrically and providing the fine powder pipe having an through-cut grooves to obtain a Coanda effect from the jet nozzle.

CONSTITUTION: A supply pipe 21 connecting to a raw material supply part, the cylindrical face 23 opening through-grooves 22 starting radially from the inner wall of the supply pipe 21 as a plural jet nozzles 24, and the coarse powder pipe 27 connecting to a coarse powder recovering part are assembled concentrically. The same number of fine powder pipes 25 consisting of the outer peripheral surface where the direction of an opening is nearly a tangent are rotatably engaged to the outer circumference of the cylinder face 23. In the fine powder pipes 25, the cut grooves 26 passing through respectively are open and all pipe insides are communicated with a fine powder recovering part. Namely, by utilizing a Coanda effect being without necessitating a high speed rotation, a highly accurate classification effect on superfine powder of a submicron size is obtained.