The hydraulic jack comprises a casing (1) with a face cover (2) and a back cover (3) and a piston rod (4) moving in relation to each other, on which rod there are provided a sealing element (7) and at least two grooves to form a corresponding rib (8). On each of said grooves, piston semi-rings (6) are arranged pairwise, and thus the portion of the rod (4) with the ribs (8) and grooves forms a piston unit (5).
