A panel structure is fabricated by stretching a skin plate with a tensile stress below the elastic limit stress thereof, securing this plate onto a framework with the plate under a constraining tensile stress and with portions thereof to which the constraining stress is not being fully applied being heated thereby to cause thermal expansion thereof, removing the constraining stress, and permitting the plate to cool and thereby to undergo thermal contraction and deformation, thereby producing tensile residual stress within the plate, whereby occurrence of welding deformations in the plate on the finished panel is prevented. Depending on the necessity, the skin plate may be prestretched with a stress exceeding the yield point thereof before the above described panel fabrication.