To provide a volume reducing and solidifying device of refuse, in which a cutting device provided with a structure free from disturbing the cutting work by a cutter even if hard refuse is contained in the melted and kneaded and continuously extruded molten refuse.

This treating device is constituted of a hopper 1 provided with a preliminary screw for previously kneading the charged refuse and a plasticizing and extruding device 5 provided with a main screw 9 for melting and kneading the refuse sent from the hopper 1 through the pre-screw in a heating cylinder and for discharging forward and a cutting device 10 for cutting the molten, kneaded and continuous refuse extruded from an extruding port of the device 5 into a desired size in the front of the device 5 to reduce the volume of the refuse, solidify and discharge and the cutting device 10 is provided with vertically movable cutting blades 11 and 13 in the front of the extruding port 8 of the plasticizing and extruding device 5 and a clearance is optionally formed between the cutting blades 11 and 13 and the extruding port 8 to vertically move the cutting blades 11 and 13.