NOVELTY - A multilayer stainless steel clad steel raw material includes stainless steel having 0-0.3 mass% of boron as inner layer and stainless steel having 0.3-2.5 mass% of boron as outer layer joined by stainless steel weld metal including chromium, silicon, molybdenum, nickel, carbon, nitrogen and manganese. The content of chromium, silicon, molybdenum, nickel, carbon, nitrogen and manganese in weld metal satisfies relations (1) and (2).    USE - Multilayer stainless steel clad steel raw material is used for manufacture of multilayer stainless-clad-steel thick board and manufacture of multilayered stainless clad steel used for separator of polymer electrolyte fuel cell (all claimed).    ADVANTAGE - The multilayered stainless clad steel is manufactured economically in high yield by using the raw material, and has excellent moldability and hot-working property. The polymer electrolyte fuel cell is manufactured efficiently, and provides excellent battery performance.    DETAILED DESCRIPTION - A multilayer stainless steel clad steel raw material has stainless steel having 0-0.3 mass% of boron as inner layer and stainless steel having 0.3-2.5 mass% of boron as outer layer joined by stainless steel weld metal containing chromium (Cr), silicon (Si), molybdenum (Mo), nickel (Ni), carbon (C), nitrogen (N) and manganese (Mn). The content of chromium, silicon, molybdenum, nickel, carbon, nitrogen and manganese in weld metal satisfies relations: Creq=15-30 (1), and Creq-Nieq=4-17 (2), where Creq=Cr+1.5x Si+Mo-5x B, Nieq=Ni+30x (C+N)+0.5x Mn, and the content of elements contained in the steel is in mass%. INDEPENDENT CLAIMS are included for the following:    (1) manufacture of multilayer stainless steel clad steel raw material;    (2) manufacture of multilayer stainless-clad-steel thick board; and    (3) manufacture of multilayered stainless clad steel.    DESCRIPTION OF DRAWING(S) - The drawing shows the graph illustrating transition of deformation resistance in multilayered-clad steel plate. (Drawing includes non-English language text)