Method and apparatus for the continuous industrial production of tubular bodies in which coated or uncoated steel strip is formed to a slit tube and the opposite strip edges are longitudinally seam welded at high speed by a laser beam of high energy density under protective gas with or without supply of additive material, and after a preparation adapted to the narrow melt zone and bringing together of the strip edges a fusion welding with subsequent controlled cooling and upsetting is carried out which results in a seam geometry suitable for any further processing.