An ultrasonic sealing device, comprising: - an electrical signal generator; - a converter for converting the electrical signals into mechanical vibrations; - a sonotrode rotating about a first axis and having a first peripheral surface; and - an anvil rotating about a second axis parallel to the first axis and having a second peripheral surface; wherein: - one between the first peripheral surface and the second peripheral surface has a circular groove; and - one between the second peripheral surface and the first peripheral surface, respectively, has a protruding element which is annular in shape; the protruding element being configured to engage the groove for a predetermined depth and operating in conjunction at least axially along directions parallel to the first axis and to the second axis with the groove, in such a way as to seal a material to be sealed, the material being moved along a direction transversal to the first and second axis and passing between the sonotrode and the anvil engaging the groove and the protruding element; characterised in that: - the protruding element and the groove have respective geometrical configurations, in cross-section, which are different; and - the protruding element has a geometrical configuration, in cross-section, which is able to penetrate into the groove by the depth which is less than the maximum depth of the groove. - an electrical signal generator; - a converter for converting the electrical signals into mechanical vibrations; - a sonotrode rotating about a first axis and having a first peripheral surface; and - an anvil rotating about a second axis parallel to the first axis and having a second peripheral surface; wherein: - one between the first peripheral surface and the second peripheral surface has a circular groove; and - one between the second peripheral surface and the first peripheral surface, respectively, has a protruding element which is annular in shape; the protruding element being configured to engage the groove for a predetermined depth and operating in conjunction at least axially along directions parallel to the first axis and to the second axis with the groove, in such a way as to seal a material to be sealed, the material being moved along a direction transversal to the first and second axis and passing between the sonotrode and the anvil engaging the groove and the protruding element; - one between the first peripheral surface and the second peripheral surface has a circular groove; and - one between the second peripheral surface and the first peripheral surface, respectively, has a protruding element which is annular in shape; the protruding element being configured to engage the groove for a predetermined depth and operating in conjunction at least axially along directions parallel to the first axis and to the second axis with the groove, in such a way as to seal a material to be sealed, the material being moved along a direction transversal to the first and second axis and passing between the sonotrode and the anvil engaging the groove and the protruding element; - the protruding element and the groove have respective geometrical configurations, in cross-section, which are different; and - the protruding element has a geometrical configuration, in cross-section, which is able to penetrate into the groove by the depth which is less than the maximum depth of the groove.