To provide a package bag usable for boiling-sterilization.

The package bag (10) with a back seal part packaging foods and heated by a microwave oven comprises a laminated film (11) made by laminating a non-stretched polyethylene film layer (13) with a base material layer (12). A seal part for opening (22) which is peelable and openable by the internal pressure of the package bag formed at part area of the back seal part (21) with a narrow seal width, is provided. And, also, at the back seal part, an easily-peelable insertion tape (30) on the one side of which a non- stretched polyethylene film layer of cohesion-destruction type (31a) is inserted in the whole area projected inside of the package bag body other than the back seal part.