NOVELTY - A case (1) comprises a container (21) having opening, a cover component (31) fitted by opening and welded to a opening peripheral portion (25) which regulates the opening, and a welding portion (41) formed by melting a portion of opening peripheral portion and a portion of cover component, and connects the opening peripheral portion and the cover component. The welding portion comprises a metal (45) having hardness more than the metal material of the container and the metal material of the cover component.    USE - Case is used for nonaqueous electrolyte secondary battery (claimed) used as power supply for hybrid vehicles, electric vehicles and factories, and domestic power supply.    ADVANTAGE - The case has excellent pressure resistance, and suppressed fluctuation in the welding strength of opening peripheral portion and cover component portion.    DETAILED DESCRIPTION - A case comprises a container having opening, a cover component fitted by opening and welded to a opening peripheral portion which regulates the opening, and a welding portion formed by melting a portion of opening peripheral portion and a portion of cover component, and connects the opening peripheral portion and the cover component. The welding portion comprises a metal having hardness more than the metal material of the container and the metal material of the cover component. The metal is provided in internal peripheral surface of the opening peripheral portion or outer peripheral surface of the cover component in a state of crystal structure which exhibits a lubricous effect. The metal is incorporated in the welding portion by melting a portion of opening peripheral portion or portion of cover component and dispersing. An INDEPENDENT CLAIM is included for manufacture of nonaqueous electrolyte secondary battery.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the case.    Battery case (1)    Container (21)    Opening peripheral portion (25)    Cover component (31)    Welding portion (41)    Metal (45)