The present invention provides a structural body comprising a welded portion of a duplex stainless steel inclusive of an α phase and a Υ phase and an unwelded portion of the duplex stainless steel, wherein an X-ray diffraction intensity for the α phase is higher in a heat affected zone including the welded portion than in the unwelded portion and becomes a local maximum within the heat affected zone. The present invention provides aA production method for a structural body of a duplex stainless steel, wherein a heat affected zone including a welded portion of the structural body is heat-treated between 600° C. and 800° C. while a magnetic field of 1˜10 T is applied to the heat affected zone.