An air classifier comprises a casing (1) formed of a generally hollow cylindrical vertical cassing body (2) and an inverted conical hopper (3) fixed to the lower wall of the casing body (2). A fine product outlet duct (6) is provided at the center of the upper wall of the casing body (2). An air-powdered material inlet duct (4) and a secondary air inlet duct (5) are set in the diametrically opposite positions of the vertical wall of the casing body (2) to project tangentially outward. A vertical rotary shaft (7) extends through the central portion of the casing body (2). A rotary disc member (8) for concurrently carrying out the dispersion and classification of a powder raw material is fitted to the lower end of the rotary shaft (7) at a boundary between the casing body (2) and hopper (3). A cage-shaped assembly of guide vanes (11) is provided in the casing body (2) to conduct a mixture of air and powdered material into the casing body (2). The air classifier of this invention constructed as described above can precisely classify by itself a large amount of powder material as a classifier for swept-air from a mill.
