NOVELTY - The device has an exterior body for enclosing a positive electrode (201), a negative electrode and electrolyte and comprising a first region with curved shape, wavy line shape, arc shape or shape with inflection points and a second region with same shape as the first region, where the first region and the second region are in contact with each other. The electrolyte comprises electrolyte solution and gelled high-molecular material. The exterior body comprises a polymer film.    USE - Flexible power storage device i.e. flexible lithium-ion secondary battery, for an electronic device (claimed) such as cameras e.g. digital cameras and digital video cameras, digital photo frames, portable game consoles, portable information terminals e.g. cellular phones, smartphones, and laptop personal computers, and audio reproducing devices i.e. portable music players. Can also be used for a lead storage battery, a lithium-ion polymer secondary battery, a nickel-hydrogen storage battery, a nickel-cadmium storage battery, a nickel-iron storage battery, a nickel-zinc storage battery, a silver oxide-zinc storage battery, a solid-state battery and an air battery for a medical equipment and next-generation clean energy vehicles such as hybrid electric vehicles (HEVs), electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs).    ADVANTAGE - The device includes a wavy sealing portion with total length larger than a linear sealing portion to increase adhesion, so that highly reliable secondary battery that can endure repeated deformation can be obtained. The battery ensures a sealing structure with high durability since the wavy sealing portion has better adhesion than the linear sealing portion and is not easily broken by stresses. The device includes a bent portion that can relax stress due to external force applied after fabrication of the secondary battery, so that reliability of the secondary battery can be increased.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of a secondary battery.    Positive electrode (201)    Positive electrode current collector (201a)    Positive electrode active material layer (201b)    Negative electrode active material layer (202b)    Separator (203)