Semi-Automatic carton sealer with auto-adhesive tape for the top and bottom sealing of American-type medium and large boxes, for uniform carton size batches with manual dimensioning. The upper taping unit has a patented system which, be regulating a spring, enables the subsequent weight on the box to be present and therefore any differences in height of the boxes to be absorbed. The boxes are fed by lateral conveyor belts, driven by a single motor thus optimizing even sliding of the boxes and ensuring perfect alignment of the upper and lower flaps which is turn guarantees perfect dealing. The adjustments are fast and easy by means of hand wheels, also allowing its use by non-specialist operators. The machine, if combined with in-feed and out-feed conveyors, represents a simple, fast and economical packaging station.