A pouch comprises a plurality of plastic sheets sealed on periphery, has a contents spout and a plastic zipper arranged in a fused state between the sheets whose outer periphery is sealed, and is heat-sterilized after being filled with contents. A a barrier portion is formed in a portion of the pouch interior set further toward the contents and away from the plastic zipper, the barrier portion formed in a state in which a film base material has been folded over. As a result, even if any damage is imparted during the step for manufacturing the plastic zipper or the step for mounting the zipper in the pouch, there will be no incidence of the contents leaking from the barrier portion and reaching the zipper portion due to heat and pressure encountered when retort sterilization, boiling, or another type of heat sterilization is performed after the pouch has been filled with foodstuffs or other material.