The utility model provides a deviation correcting device is trailed to the built-in joint strip of envelope in the bag-making machine is at the automatic tracking self-corrective measures of the boiling hot sword of bag-making machine operation in-process realization, joint strip. This installation of automated degree is high, and deviation rectifying effect is good, guarantees product quality, has improved system bag production efficiency. Two ends that seal boiling hot sword during the bag-making machine includes, horizontal linear guide is vice and push down drive mechanism perpendicularly seal boiling hot sword in, are connected with horizontal linear guide is vice, and vice two ends of horizontal linear guide are connected with the perpendicular drive mechanism of pushing down, and tracking deviation correcting device includes can move horizontal axis, joint strip deflector, photoelectric sensor, can move the horizontal axis and be on a parallel with said horizontal linear guide is vice to be provided, can move installation guide pillar seat on the horizontal axis, joint strip deflector and photoelectric sensor, the vertical guide pillar that is provided with on the guide pillar seat, and the cover is equipped with the linear bearing seat that can follow its upper and lower motion on the guide pillar, and the linear bearing seat is installed on the connecting plate, and the connecting plate seals boiling hot sword in with and links to each other, joint strip deflector, photoelectric sensor seal a boiling hot cutter spacing in and put correspondingly.