The invention provides a machining device for urine bag and urine guiding bag backflow prevention pieces. The machining device comprises a machine frame. The machine frame comprises a bottom frame and a bottom plate. The bottom plate is fixed on the bottom frame through a bottom plate clamping buckle. One side of the bottom frame is provided with a scroll clamping disc. One end of the bottom plate is provided with a feeding air cylinder. The scroll clamping disc and the feeding air cylinder forms an automatic feeding mechanism. The bottom plate is further provided with an automatic traction mechanism, an automatic cutting mechanism and an automatic welding mechanism. The automatic traction mechanism is arranged on one side of the feeding air cylinder. The automatic cutting mechanism is arranged between the automatic traction mechanism and the automatic welding mechanism. The automatic welding mechanism is arranged at the other end of the bottom plate. The machining device has the following advantages that 1, cutting is more orderly by using spring pressing film pieces with vacuum, and the welded and formed backflow prevention pieces are more smooth; 2, shapes of an upper electrode and a lower electrode can be replaced at will, and the backflow prevention pieces of various shapes are welded; and 3, the air tightness of the formed backflow prevention pieces is higher.