The invention discloses a processing device and method for producing flat yarns. The device comprises an input roller used for inputting core yarns, a parallel arrangement yarn guide arranged above the input roller, a ring arranged above the parallel arrangement yarn guide and used for accommodating covering yarns, a flat yarn guide hole type yarn guide arranged above the ring, and an output roller arranged above the flat yarn guide hole type yarn guide, wherein the parallel arrangement yarn guide is provided with at least three first yarn guide holes arranged in parallel, the ring is provided with a ring center hole, the flat yarn guide hole type yarn guide is provided with a second yarn guide hole, the first yarn guide holes are matched with the ring center hole, and the ring center hole is matched with the second yarn guide hole. By the adoption of the structure, a plurality of core yarns can pass through yarn guiding devices arranged in parallel so as to enter a twisting system in parallel; meanwhile, the flat yarn guide hole type yarn guide is adopted for an output yarn guiding device, so that it is guaranteed that the core yarns are arranged in parallel when fixed by the covering yarns.