The invention discloses a steel pipe welding device. The welding device comprises a shell, a welding mechanism and a clamping mechanism, wherein a rotary cylinder is arranged in the shell, the weldingmechanism is arranged on the rotary cylinder and comprises a set of welding guns which are oppositely arranged, the welding guns are fixedly connected with lifting frames, sliding groove plates are embedded in the upper ends of the lifting frames, the rotary cylinder is fixedly connected to the inner sides of the sliding groove plates, the rotary cylinder is fixedly sleeved with a gear ring, thegear ring is meshed with a driving gear, and the driving gear is fixedly connected with a driving motor. According to the welding device, by arranging a rotating structure comprising the rotating cylinder, the gear ring and the driving gear, a steel pipe is annularly welded, and compared with manual welding, the efficiency is high, and the quality is good; by arranging the sliding groove plates, lead screws, rotating wheels and the lifting frames, the height of the welding guns is conveniently adjusted, welding of steel pipes of different diameter specifications is achieved, and adaptability is good; and by arranging clamping plates, two-way lead screws, the double-shaft motor and supporting rollers, the levelness and stability during steel pipe welding are improved.