For the cruciform welded joints between corrugated bulkhead of Duplex stainless steel plate and inner bottom of stainless (SUS) clad steel plate under biaxial tensile loading condition, numerical analysis of finite element method were performed with changing the loading condition, fillet size and welding condition of penetration. The stress concentration on each weld toe of the cruciform welded joints was evaluated. As results, the geometrical symmetry between upper and lower side welded joint shape on inner bottom plate of cruciform welded joint is important to prevent high stress concentration under biaxial tensile loading condition and partial penetration weld is effective to suppress stress concentration from comparison with fillet weld.