PURPOSE: To make it possible to control the titled dust generating speed under a same amount of a gas, by a method wherein a particulate material and fine particles on a dispersing plate are fluidized by a gas and only fine particles are generated from a fluidized layer as well as the generating speed thereof is controlled by electric force.

CONSTITUTION: A particulate material and fine particles having a particle size considerably larger than that of the former are accumulated on a dispersing plate 1 provided to the bottom part of a fluidized layer type dust generating apparatus and a gas is blown thereinto from the lower part of the dispersing plate 1 as shown by an arrow G to from a fluidized layer 3. In this case, only fine particles are flied out to generate fluidized layer dust. On the other hand, high voltage is applied between a discharge electrode 4 provided to the inside of the fluidized layer type dust generating apparatus and an earth electrode 5 of the outer periphery thereof. When said high voltage is applied, fine particles flied out from the fluidized layer 3 are accompanied between the electrodes 4, 5 by the gas and, while carried as generated dust as shown by an arrow D, collected to the electrode by electric force. Therefore, by appropriately controlling the applied voltage, the generation concn. of the fluidized layer dust can be varied.