To provide a small and light-weight secondary battery having superior airtightness.

This secondary battery has a bag body 6 for storing an electrolyte, formed of a protective layer, a water vapor impermeable layer, an electric insulation layer and an adhesive layer respectively in order from the outside, and a tape type metallic terminals 4 are clamped with the adhesive layer and welded to the mouth 6a of the bag body 6. In this case, the adhesive layer is made of polyolefine based resin having a polar group.