To develop a packaging bag from which gas can be safely vented when the inner pressure therein rises to a dangerous level, while it is enclosed airtight under normal conditions.

In the gas venting packaging bag formed from a composite film made of a plurality of polyolefin-based films bonded together, holes are provided at given positions on an inner side film on the opposite side of outside air as a gas venting structure, the location having these holes has a structure enclosed by a polymer adhesive, thus providing a gas venting structure wherein the polymer adhesive and the inner side film are separated when gas pressure rises, thereby air-vent holes are formed for venting gas and furthermore gas outlet openings are formed. In particular, it is so constituted that, (a) when the packaging bag is made, the polymer adhesive is applied to the inner side film which does not come in contact with outside air, (b) a hole A is bored through the polymer adhesive applied section and the inner side film, and (c) an outside film which is in contact with outside air is overlapped over the hole A so as to enclose the hole A, as it is bonded with the polymer adhesive, and simultaneously, in areas where the adhesive does not exist, the outside film and the inside film are bonded.