The invention discloses a screw polishing device. The screw polishing device comprises a left supporting frame, a limiting ring, a machined screw, a polishing device body, polishing pulleys, a polishing belt, a fixing device, a polishing motor, a fixing plate, a connecting rod, a cleaning device, a fixing rod, a water inlet device, a spray gun, a hydraulic cylinder, a hydraulic pump, a movable pulley device, a first pulley block, a second pulley block, a first pulley motor, a second pulley motor, a sliding rail, a right supporting frame, an automatic telescopic rod, a positioning rod, a drivenwheel, a driving wheel, a rotating motor and a control device. The screw polishing device has the advantages that the device is mechanical and electrical integrated equipment, and automatic operationcan be achieved; during polishing, the polishing belt is in close contact with a screw through the fixing device, the polishing smoothness can be controlled, the tolerance of the screw is well kept,and the polishing precision of the screw is improved; and after polishing is completed, the spray gun on the cleaning device synchronously cleans the abrasive attached to the surface of the screw, sothat polishing operation and cleaning operation are completed at a time, the screw treatment procedure is simplified, and time is saved.