Manufacturing method of power storage device

A manufacturing method of a power storage device, the manufacturing method comprising:

• an arrangement step of arranging a first resin member that contains a thermoplastic resin and that transmits an electromagnetic wave, on a first surface of a metal foil with a thickness of 1 μm or more and 100 μm or less, the first resin member being arranged such that an end portion of the first resin member is longer than an end portion of the metal foil, and arranging a second resin member that contains a thermoplastic resin and that transmits an electromagnetic wave, on a second surface of the metal foil, the second resin member being arranged such that an end portion of the second resin member is longer than the end portion of the metal foil;
• and
• a welding step of arranging a first pressurizing member that transmits an electromagnetic wave on a surface on an opposite side of the first resin member from a surface on the metal foil side, arranging a second pressurizing member that transmits an electromagnetic wave on a surface on an opposite side of the second resin member from a surface on the metal foil side, and irradiating the end portion of the metal foil with an electromagnetic wave from the first pressurizing member side while pressurizing the end portion with the first pressurizing member and the second pressurizing member so as to weld the first resin member and the second resin member to the metal foil such that the end portion of the metal foil is covered.