Abstract: An object of the present invention is to provide a bag which enables refilling of a container from the bag to be carried out smoothly, without the contents coming out of the pouring mouth all at once and without the bag losing its shape, and the pouring mouth to be set to a certain specific size; which eliminates the need of a special sealing device; and which is strong. Further, with the bag according to the invention, the refilling can be carried out easily, without scissors or the like being required for forming the pouring mouth, the overall shape of the bag does not have to be made long in the vertical direction; and without any of the contents remaining in the bag during pouring.