A battery includes an outer package including a laminated film including one or more resin layers, a terminal, and a melt-bonding assisting member including a thermoplastic resin and extending along the terminal. The outer package includes a melt-bonded region at which the terminal is sandwiched between the one or more resin layers. The terminal includes an inner part, a sandwiched part, and an outer part arranged in a first direction. The melt-bonding assisting member internally and externally extends in the first direction beyond contact with the outer package.