Abstract: A lithium-ion secondary-battery case that allows bonding without weld spatter and has high strength against external force acting on the battery case, and a method for manufacturing the lithium-ion secondary-battery case are provided. Specifically, an austenitic stainless steel foil is used for a cup component (2), and a two-phase stainless steel having an austenite transformation start temperature AC1 in a temperature increase process at 650° C. to 950° C. and an austenite and ferrite two-phase temperature range of 880° C. and higher, is used for a cover component (3), and the diffusion bonding is proceeded while accompanied by grain boundary movement upon transformation of the two-phase steel from a ferrite phase into an austenite phase within a heating temperature range of 880° C. to 1080° C.