To provide a crusher which can finely size-reduce plastics and the like in a short time without generating a loud noise and has excellent processing capacity.

Sawing blades of each circular sawing plate in a sawing plate assembly 15 mounted on a major axis 14 driven by a motor 3 are bent in an axial direction with varied angles so that the positions of blade edges are successively shifted to bring the blade edge trajectory to a multiplexed state in a fine pitch. Further, a first receiving blade 53 and a second receiving blade 54 are disposed so as to sandwich therebetween a discharge part 10, located below the sawing plate assembly 15, before and behind the discharge part 10. A material to be treated is sawed and cut by the sawing blade in the sawing plate assembly 15 and the first receiving blade 53 to size-reduce the material. The crushed material is further sawn and cut at the position of the second receiving blade 54 for further crushing and the crushed material is dropped through a screen 61 and is then discharged.