An apparatus for ring-sealing closure means (200) on respective containers (100) and provided with rotating turret means (2), for supporting and holding containers (100) and the respective closure means (200), and comprising ring- sealing means (4) movable in relation to containers (100) for deforming an edge of closure means (200) on the periphery of the necks of containers (100); the ring-sealing means (4) is engaged with cam means (70) by means of articulated means (5); the cam means (70) is movable in relation to turret means (2) along a direction of adjustment (Z) for adjusting a position of ring- sealing means (4) in relation to containers (100) and comprises a cylindrical cam.