To prevent breakage of a bag at a change of shape after filling and packaging, to eliminate troubles of enticing bugs and being torn up by them during processes of distribution and to prevent dirt and dust from collecting into the bag by a method wherein air vents are arranged zigzag at two stripes of heat sealing line provided along the side at opening end of the bag.

For a bagging-type package body that is made up by filling a plastic bag 1 with its one end opened with sugar or the like at a fixed quantity of filling and by sealing up the inside of the bag 1 with heat sealing lines 11 along the side at the opening end of the bag 1, the heat sealing line 11 is provided at least in two stripes with an interval provided from the inside toward the opening end of the bag 1. Then, a plurality of air vents 12 permitting air to penetrate through the opening end from the inside of the bag 1 to the outside are formed intermittently along the extending direction of the heat sealing lines and at the same time, the air vents 12 formed at the adjoining heat sealing lines 11 are arranged zigzag with each of their positions being offset in the direction of extension and thereby a kind of labyrinth seal is constructed.