PURPOSE: To efficiently separate materials and reduce the size of a wind pressure separator by a method wherein the separator is so constructed as to apply air pressure in a lower pressure direction by the rotation of a fan.

CONSTITUTION: Upon air supply by a fan in the position A, the air pressure is applied uniformly from B to above C and D under lower pressure due to a small space of a coil 15 and the powder to be separated dropping from an end E of the coil 15 is forced up and sent forward by the air pressure. At this time, of the powder, the cakes are blown not far off but the light one is sent at a greater distance. In doing so, the powder is efficiently separated according to the mass differences.