A power storage device packaging material including a base material layer; an adhesion-enhancing treatment layer on a surface of the base material layer; an adhesive layer on a surface of the adhesion-enhancing treatment layer opposite the base material layer; a metal foil layer formed on one side of the adhesive layer opposite the adhesion-enhancing treatment layer; and a sealant layer disposed on a surface of the metal foil layer opposite the adhesive layer. The base material layer is formed of a biaxially oriented film to have a breaking strength of 240 MPa or more in at least one of four directions (0° (MD), 45°, 90° (TD), 135°) and an elongation of 80% or more in at least one direction in a tensile test (test specimen shape: test specimen type 5 stipulated in JIS K7127; inter-chuck distance: 60 mm; tensile speed: 50 mm/min).