Abstract: There is described a device for welding motor-vehicle bodies, comprising a welding station provided with welding programmable robots, to which the floor panels of the bodies to be welded are fed along a vertical direction by a lifting device. The component elements of the sides of the body to be welded are brought to the assembling position by means of two locating gates, provided with self-propelled lower carriages, which are movable on rails between a working position, at the two sides of the floor panel of the body to be welded, and a waiting position, in which they may receive the component elements of the body sides. The elements of the rear part of the body are carried by a third locating frame arranged transversally between the two guiding rails of the side locating gates.