LAMINATE

A laminate for forming a packaging bag, in sequence: a substrate layer; an adhesive layer; and a sealant layer, wherein the sealant layer includes a first polyester film having a crystallinity of 20 to 50% based on a first absorbance at a first wavenumber of 1409 cm−1, a second absorbance at a second wavenumber of 1370 cm−1, a third absorbance at a third wavenumber of 1340 cm−1, a first constant, and a second constant, the first to third absorbances and the first and second constants being determined based on FT-IR analysis, which uses a reflection method, on at least the first polyester film, the crystallinity of the first polyester film being expressed in accordance with the following formulas (1) and (2): I1409=p1×I1340+p2×I1370 . . . (Formula 1) and C=p1×(I1340/I1409)×100 . . . (Formula 2).