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. IMAGE
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