Tamping machine (1), particularly for regenerating railway ballasts, comprising: a supporting frame (2), at least one vibrating tamping hammer (3) pivoted to the frame (2), a hydraulic actuator (4) engaged with a thrusting portion (3b) of the tamping hammer (3), the actuator (3) comprises a first and second axially aligned sections (5, 6) engaged with each other, one of said first and second sections (5, 6) is engaged with the thrusting portion (3b) of the tamping hammer (3), while the other section is engaged with an abutment portion; the first section (5) is extendable while the second section (6) is configured for being supplied by distributing means having an alternate cyclical operation for enabling the tamping hammer (3) to vibrate. The second section (6) comprises a jacket (7) extending between a first and second longitudinal ends (7a, 7b), and a piston (8) slidingly movable inside the jacket (7). The jacket (7) is closed at the first and second longitudinal ends (7a, 7b); the piston (8) exhibits an overall axial size defined by respective thrusting opposite faces of the piston (8) itself which is entirely contained inside the jacket (7).