A laminate packaging flat cell comprises a laminate film formed by combining polymer and metal with each other; a power generating element formed of a plurality of electrode plates and separators, and hermetically sealed by the laminate film; and an electrode terminal lead coupled to the electrode plate. In the laminate packaging flat cell of the present invention, the power generating element is hermetically sealed by forming a thermally welded portion on an outer periphery of the laminate film, and the electrode terminal lead protrudes from the thermally welded portion, and a through-hole is provided in a position thereof contacting the thermally welded portion.