PURPOSE: To avoid the need for troublesome operations such as positional matching, etc., in the formation of a bag, simplify the bag forming operation with improved efficiency and facilitate the opening of the bag thus formed, particularly by tearing easily from any position of peripheral side edges of the bag.

CONSTITUTION: A packaging sheet material is of a laminated sheet consisting of a base material layer 1 made mainly of synthetic resin film and a seal material layer 2 and the base material layer 1 is provided with fine cuts 5 in an infinite number entirely over its surface. In the base material layer 1 consisting of an outer layer base material 3 made mainly of synthetic resin film and an intermediate base material 4 of one or more layers, at least one film layer of the outer layer base material 3 and the intermediate base material 4 is provided with fine cuts 5 in an infinite number entirely over its surface. Such a packaging sheet material A is formed into a sealed bag with the seal material layer 2 inside by a heat sealing means.