Abstract: Precise classifying of granular or powdered raw material at the desired classifying point by means of a vortex pneumatic classifier comprising: a rotor, a plurality of vortex flow adjusting vanes provided on the said rotor, a classifying chamber defined around the said vortex flow adjusting vanes, and guide vanes radially opposing the said vortex flow adjusting vanes across the said classifying chamber, wherein the mounting pitch P of the said vortex flow adjusting vanes is determined in relation to the classifying particle diameter Dp(th) so as to meet the condition of the following relation expressionP.ltoreq.1.04.times.Dp(th).sup.0.365.