Abstract: The material supplied to the interior of the crushing tank by the material supply device is: crushed into the form of a fine powder by the agitator; sent upward by a gas to be directed to the classifier through the guide device; classified in the course to the classifier and the fine powder reduced to a predetermined particle size is extracted to the outside by means of the fine powder discharge tube. On the other hand, the coarse powder of which the particle size has not been reduced to the predetermined particle size is guided again to the crushing tank through a ring-like circulation passage formed between the inner peripheral surface of the communicating portion of the classifier and the outer peripheral surface of the dispersing tube of the guide device so as to be crushed by the agitator. Since this process is repeated, a fine powder of the predetermined particle size is obtained.