The invention discloses a farm excrement processing device. The farm excrement processing device comprises a preprocessing assembly, a driving motor, a processing assembly, a collecting box, a PLC andan electric control cabinet and is characterized in that the processing assembly is arranged, excrement on a conveying belt is flattened through a scraper blade, the excrement is sterilized and disinfected through an ultraviolet lamp, and a heating piece is powered on to operate to dry the excrement; compared with the mode of drying the excrement in the open air, the excrement processing efficiency and processing quality are improved, and a large amount of labor force and time are saved; by arranging the preprocessing assembly, the excrement enters a preprocessing box from a feeding port, solid-liquid separation of the excrement is achieved through a filter screen, waste liquid in the excrement flows into the lower portion of the interior of the preprocessing box, the excrement falls ontothe conveying belt of the processing box, and excrement processing operation is facilitated; by arranging a filter assembly, the driving motor drives a cam to rotate, the cam periodically impacts a left end plate, particles attached to the upper portion of the filter screen move downwards, and the phenomenon that the filter screen is blocked is avoided.