A vortex type air classifier comprises a rotor provided with a plurality of vortex controlling blades, and guide vanes provided about the outer peripheries of the blades with a classification chamber therebetween. A setting pitch P is found by the following expression in relation to separated particle sizes Dp (th), so that powder materials are accurately classified at a desired point of classification: P </= 1.04 x Dp(th)<0.365>.
