NOVELTY - The battery (10) has a housing (21) that accommodates an electrode group (22) and an electrolyte solution. A first wall is provided in the housing. A second wall is provided with a surface and welded to first wall. A welded unit (60) is appeared while providing in the housing, and an outer edge. The welded unit is provided with the welding portions (61,62) so that the welding portion (62) is provided closer to an outer edge than the welding portion (61) so as to partially overlap with the welding portion (61) respectively.    USE - Battery such as lithium ion battery for electric-power-assisted bicycle, hybrid electric vehicle, and electric vehicle, mobile telephone, personal computer, and portable music player.    ADVANTAGE - The welded unit is provided with the welding portions so that the second welding portion is provided closer to an outer edge than the first welding portion so as to partially overlap with the first welding portion respectively so that the microcrack is disappeared by the second welding portion even when microcrack arises in the first welding portion and the width of welding unit is narrowed even when the thickness of side wall is small so as to rigidly weld the container and the cover case to suppress the arise of weld flaw shaped microcrack to the welding unit by reducing the energy used for welding the second welding portion. Thus, the sealing property of the welded unit of battery is improved effectively while suppressing the leakage of electrolyte solution accommodated in the accommodating unit besides the battery and improving the durability of welding unit. Hence, the reliability and quality of the battery are improved while reducing the manufacturing cost of battery.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for manufacturing battery.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the battery.    Battery (10)    Housing of battery (21)    Electrode group (22)    Welded unit (60,70)    Welding portions (61,62)