Abstract: An automatic welding machine for waterproof sheeting with a pressing device for pressing lap-welded materials, where the pressing device has at least one press roll which is mounted on a shaft that is secured and is provided with an elastic sheathing on the circumference as a press surface on the contact surface of the material. The press roll is mounted by a pendulum bearing on the shaft which is centered with respect to the outside edges of the press surface and permits an additional limited pendulum movement of the press roll with respect to the shaft. The press roll remains parallel to the running gear of the automatic welding machine, but it can execute a pendulum movement on the basis of irregularities in the substrate, so that the pressure remains essentially constant even if the automatic welding machine is arranged at an inclination. In addition, the proposed press roll can also be driven by providing a rotationally fixed entraining unit between a drive shaft and the press roll.