A sealing device for a pouched strip to a cladding film such as to obtain a blister strip, the pouched strip being advanced in an advancement direction along a horizontal advancement tract and the cladding film being applied on the pouched strip during advancement thereof along the horizontal advancement tract, comprising: a sliding element, arranged in the advancement direction of the pouched strip and the cladding film, for sliding the blister strip released by the pair of heat-welding plates, the sliding element being provided with a curved sliding surface for the blister strip; means for forcing the blister strip to slide along, and in contact with, the curved sliding surface of the sliding element; and means for directing at least a cooling fluid to cross the sliding element in order to cool the blister strip during sliding thereof along the curved sliding surface, characterised in that it comprises: a pair of heat-welding plates arranged opposite one another and cyclically movable in such a way as to reciprocally lock in order to clamp the pouched strip and the cladding film applied thereon together in order to perform a reciprocal sealing thereof by heat-welding and obtain a blister strip and then distanced in order to release the blister strip, the lower plate of the pair of plates exhibiting recesses of a suitable shape for housing and receiving the pouches of the pouched strip when the plates are locked together to clamp the pouched strip and the cladding film, wherein the sliding element is arranged consecutively to the pair of heat-welding plates and wherein the means for forcing the blister strip to slide along and in contact with the curved sliding surface of the sliding element comprise at least a pliers gripping organ arranged laterally to the sliding element and predisposed in such a way as to be movable alternatingly with respect to the sliding element in order to follow an extension of the curved sliding surface, the pliers gripping organ being commandable to be arranged laterally and at a start of the curved sliding surface, to clamp the blister strip released by the pair of heat-welding plates and to accompany the blister strip in sliding along at least a part of the curved sliding surface. a sliding element, arranged in the advancement direction of the pouched strip and the cladding film, for sliding the blister strip released by the pair of heat-welding plates, the sliding element being provided with a curved sliding surface for the blister strip; means for forcing the blister strip to slide along, and in contact with, the curved sliding surface of the sliding element; and means for directing at least a cooling fluid to cross the sliding element in order to cool the blister strip during sliding thereof along the curved sliding surface, characterised in that it comprises: a pair of heat-welding plates arranged opposite one another and cyclically movable in such a way as to reciprocally lock in order to clamp the pouched strip and the cladding film applied thereon together in order to perform a reciprocal sealing thereof by heat-welding and obtain a blister strip and then distanced in order to release the blister strip, the lower plate of the pair of plates exhibiting recesses of a suitable shape for housing and receiving the pouches of the pouched strip when the plates are locked together to clamp the pouched strip and the cladding film, wherein the sliding element is arranged consecutively to the pair of heat-welding plates and wherein the means for forcing the blister strip to slide along and in contact with the curved sliding surface of the sliding element comprise at least a pliers gripping organ arranged laterally to the sliding element and predisposed in such a way as to be movable alternatingly with respect to the sliding element in order to follow an extension of the curved sliding surface, the pliers gripping organ being commandable to be arranged laterally and at a start of the curved sliding surface, to clamp the blister strip released by the pair of heat-welding plates and to accompany the blister strip in sliding along at least a part of the curved sliding surface. a pair of heat-welding plates arranged opposite one another and cyclically movable in such a way as to reciprocally lock in order to clamp the pouched strip and the cladding film applied thereon together in order to perform a reciprocal sealing thereof by heat-welding and obtain a blister strip and then distanced in order to release the blister strip, the lower plate of the pair of plates exhibiting recesses of a suitable shape for housing and receiving the pouches of the pouched strip when the plates are locked together to clamp the pouched strip and the cladding film, wherein the sliding element is arranged consecutively to the pair of heat-welding plates and wherein the means for forcing the blister strip to slide along and in contact with the curved sliding surface of the sliding element comprise at least a pliers gripping organ arranged laterally to the sliding element and predisposed in such a way as to be movable alternatingly with respect to the sliding element in order to follow an extension of the curved sliding surface, the pliers gripping organ being commandable to be arranged laterally and at a start of the curved sliding surface, to clamp the blister strip released by the pair of heat-welding plates and to accompany the blister strip in sliding along at least a part of the curved sliding surface.