A bag body is prevented from being ruptured when food inside is heated in a microwave oven. A laminated film of 2 or more layers having at least a base material layer P2 and a sealant layer P1 having heat resistance is bent into a cylindrical shape with the center of a back lining part of a bag body as a palm butt part 1 to provide a heat seal part of films facing each other at the palm butt part and heat seal parts of films facing each other at both opening ends 4, A foamed ink layer 5 containing thermally expandable microcapsules foamed by heat at the time of heat-sealing is provided on the base material layer side of the sealant layer so as to traverse from the inside to the outside of the packaging bag in a specific region of the heat seal part. Fig. 1

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