Automatic carton sealer, seal by gluing the upper flaps of boxes and cartons of American type. The whole system is adjustable to allow a quick format change, facilitated by calibrated position indicators. The sealing of the lower flaps can be integrated. The structure is in painted steel, completely inspectable, and it is complete with safety guards with access doors equipped with safety sensors according to current regulations. Fully automated work process, reducing the operator’s intervention to supply the adhesive tape and to change format with easy adjustments.