A device for filling and closing disposable bags for containing banknotes, comprises a container for the temporary housing of one or more banknotes, having side walls and a bottom with an opening for the exit of said one or more banknotes from the container, a pushing piston for pushing said one or more banknotes towards the bottom of the container, a bag made of flexible material intended to be filled with the banknotes temporarily housed in the container, which is anchored, at the edges of its mouth, to fixing pins placed in proximity of the opening in the bottom of the container, a plate which is vertically movable through controlled lowering means and placed below the container, the plate having a central slot, which is open at the top towards the container and extending vertically through the body of the plate for the insertion of a bottom portion of the bag anchored to the fixing pins, and first sealing elements placed between the container and the plate.