A rotating shaft for intermittent rotation through predetermined angles is located in parallel to a rotation shaft of a rotor holding a plurality of split mold units, and rubber cups for adhering labels are secured to the front ends of links which are swingable about pins secured to the rotating shaft. The label is positioned upon the inner walls of the split mold halves when the same are in their open state by the combination of the intermittent rotation of the rotating shaft and the swinging movement of the links. The split mold holds the label by vacuum suction and the label is fused to a product when a highly heated plastic material is applied under pressure to the inner wall of the mold. A split mold holder is constructed so that when a slider-crank mechanism in association with a cam follower is positioned to a dead position, the clamping force is applied. A large force is not applied to the cam follower held by the rotor and the rotor is driven at a constant speed, thus precisely performing the positioning for the label application.