Abstract: A packaging bag made by the use of a reinforced sheet in which non-woven cross-linked plastic sheets are inserted between cellulosic papers. The non-woven cross-linked sheet consists of split films with narrow width crossing each other laterally and longitudinally with slightly protruded intersections. The reinforced sheet is made by inserting the non-woven cross-linked sheets between cellulosic papers during paper making on a combination paper machine, thereby slightly protruded portions caused by the intersections in the non-woven sheets can be secured on the whole surface of the reinforced sheet. The bag thus manufactured using the reinforced sheet has extremely improved strength and handling properties as well as good air permeability compared with the conventional paper and plastic film bags.