The invention relates to an automatic welding tractor belonging to the field of equipment for automated welding. The automatic welding tractor has the structure that a welding gun collet is arranged on a tractor body, and the welding gun collet clamps a welding gun to take uniform motion in a straight line to weld along a welding seam; a permanent powerful magnet is arranged below the welding tractor so as to fix the welding tractor on a flat surface, and the lateral surface of the welding tractor is provided with a guide wheel which positions the welding gun and the welding seam; the weldingtractor regulates the guide wheel to enable the guide wheel to tightly attach to the lateral surface of the welding tractor along the advancing direction of the welding tractor; the welding tractor moves along the welding seam; a manual fine regulating device is arranged on the welding tractor and can regulate the distance between the welding gun and the welding seam; and a speed regulator is arranged on the welding tractor and regulates the welding speed of the welding tractor under different conditions. The invention fills up the blank of the prior art, has the advantages of simple structure, small volume, light weight, low cost, convenient carrying, good welding stability, high popularity, full automatic welding, high work efficiency, easy and convenient operation, attractive appearanceand stable quality of welded products, and is suitable for any steel structure field, such as boiler products, shipbuilding industry, and the like.