To crush to a desired particle size.

A pair of first and second crushing disks 5a, 5b are installed so as to face each other with a crushing gap 7 of a certain width D. At least one of the disks 5a, 5b is made rotary, and the second disk 5b is made movable to-and-fro relatively to the first disk 5a to make the gap width D adjustable. Thus, an object to be crushed is crushed between the rotating first and second disks 5a, 5b and simultaneously a crushing product with a small particle size is discharged through the gap 7 between the disks 5a, 5b.