A high strength clad material having excellent moldability, specifically a three-layered clad material produced by using a stainless steel as a substrate and integrating a sheet of nickel or its alloy with one principal plane of the substrate and a sheet of copper with the other principal plane of the substrate both by pressure welding or a two- or three-layered clad material produced by integrating a sheet of nickel or its alloy with at least one principal plane of the substrate by pressure welding. The clad material makes it possible to further increase the relative thickness of the stainless steel, while reducing the total thickness of the clad material, thus realizing a mechanical strength (tensile strength) at least equivalent to that of the conventional two- or three-layered clad material. A tension bridle roll having a predetermined size and shape is disposed on the feed side of a pressure welding roll and a sheet of nickel, copper, etc., is fed to the pressure welding roll through the tension bridle roll, thus making it possible to apply a uniform tension to each sheet as a whole, to prevent the occurrence of breakage and wrinkles during the pressure welding, to reduce the thicknesses of both nickel and copper sheets before pressure welding to about 5 νm, and to reduce the relative thickness of each sheet in the three-layered clad material for a battery case to about 0.5 % of the total thickness.