A labeling machine for applying tubular labels to articles; the machine comprises a conveying device movable along a given path and at least one unit to receive and retain an article to be labelled, a feeder to feed a label to the unit, a former to bend the label in a vertical tubular configuration with opposite vertical edges overlapping one another, and at least one welding device arranged on the conveying device to weld the overlapped edges of the label; the welding device comprises an electrically heatable sealing element, provided with a striplike working surface having a height at least equal to the height of the label overlapped edges to be welded, electrical power supplying means selectively connectable to the sealing element and controlled for heating the sealing element along a given portion of the mentioned path and for cooling the sealing element along a subsequent portion of the path, and actuator displacing the sealing element to and from the overlapped edges of the label along a horizontal direction transverse to the path.