Abstract: A method of manufacturing a bag from a cylindrical net-like bag blank made of synthetic fibers or synthetic resin. The method involves the steps of inserting into said bag blank a resilient plate having a length which is at least equal to the depth of the bag to be manufactured and a width which is substantially equal to the circumferential length of said bag blank in such a way that the plate is not overlapped with the bag bottom forming portion of the bag blank but is overlapped with the bag mouth forming portion of the bag blank.