This taping machine for water-activated tape has been designed for taping sets of boxes of equal size. The machine receives the filled boxes coming from one or more lines via idler or powered roller beds. The spaced insertion of the boxes, the closing of the upper flaps and the sticking on of the water-activated tape above and below are fully automatic. Operator intervention is only required to adjust the machine to the box size. This very simple operation does not take more than 60 seconds.