Welding machine for edge-side connection at the edge of overlapping material webs, wherein the materials are connectable to one another under the effect of heat and subsequent pressure, with a chassis on which at least guide rollers, a heating device and at least one pressure roller are arranged. The heating device has a cantilevered contact heating element that can be inserted laterally between the edges of the material webs, wherein the chassis is driven by an electric motor which is arranged on a longitudinal leg of the chassis. The electric motor according to the invention is formed as a brushless DC motor and the reduction gear as a planetary gear, which are united by a drum drive motor. In this case, the direct current motor is preferably a disk rotor motor. The chassis has a lateral leg which is adjustable perpendicularly to the working direction relative to the longitudinal leg.