A battery manufacturing method and a battery are provided. The battery manufacturing method includes: providing a first housing, including a bottom wall and a side wall, wherein the side wall extends upward from the bottom wall, the side wall encloses to form an opening, the side wall extends outward from the opening to form a first flange, and a first reinforcing part is formed on the first flange; providing a second housing, wherein the second housing includes an intermediate part and a second flange, the intermediate part covers the opening, and the second flange is in contact with the first flange; and welding the first flange and the second flange.