The invention relates to a mixing device, in particular to an extruding machine for extruding cellular SCR (Selective Catalytic Reduction) denitration catalyst. The extruding machine comprises a frame, and an upper layer mixing filtering part, a middle layer extruding mechanism and an extruding body which are installed on the frame, wherein the upper layer mixing filtering part and the middle layer extruding mechanism are distributed in a step way from from top to bottom; main body structures of the upper layer mixing filtering part, the middle layer extruding mechanism and the extruding body are the same and comprise screw shafts driven by motors to rotate; the screw shafts are installed inside extruding cavities used for containing materials; a material inlet is connected with the upper part of the extruding cavity of the upper layer mixing filtering part; the outlet of the extruding cavity of the upper layer mixing filtering part is connected with the extruding cavity of the middle layer extruding mechanism; the outlet of the extruding cavity of the middle layer extruding mechanism is connected with the extruding cavity of the extruding body through a vacuum box. The extruding machine is high in extruding pressure, adopts three-layer design, and can effectively filter impurities in raw materials and extrude the high-density cellular SCR denitration catalyst.