Possible to weld spatter-free bonding, and provides a lithium-ion high strength against an external force a secondary battery case and a manufacturing method applied to the battery case. That is, the cup component (2) is used to austenitic stainless steel foil, and a lid part (3) has in the austenite transformation start temperature (Ac ₁ point) in the temperature rising stage at 650 to 950 ℃, the austenite + ferrite two grain boundaries when the temperature range for the temperature range of two-phase by using a stainless steel, and contacts them directly, heating temperature 880 to 1080 ℃ having a range of more than 880 ℃, the two-phase steel ferrite phase to be transformed to the austenite phase and it characterized by while accompanied by the movement progress diffusion bonding.