The invention discloses a paper board printing device. The paper board printing device comprises a workbench. The workbench is provided with a conveying belt. The conveying belt is sequentially provided with a material box, an extrusion device, a straightening device and a printing roller. The extrusion device is arranged on one side of the material box and comprises a supporting frame I, a supporting frame II and a supporting frame III. A pressing belt I is arranged between the supporting frame I and the supporting frame II and is obliquely arranged. A pressing belt II is arranged between thesupporting frame II and the supporting frame III. One end of the pressing belt II is connected with one end of the pressing belt I through the supporting frame II. The supporting frame II and the supporting frame III are provided with sliding grooves. A supporting plate is arranged in the pressing belt II. The connecting rod is arranged between the supporting frame II and the supporting frame IIIand connected with an air cylinder. The telescopic end of the air cylinder is connected with the supporting plate. The straightening device is arranged at the bottom of the pressing belt I, and the printing roller is arranged on one side of the extrusion device. Through the arrangement of the extrusion device, paper boards can be flattened, and straightening device is matched, so that the printing effect is better.