Abstract: A hydraulic actuator (1) comprising a body (2), in which a control arm (5) and a lift means (6) provided with a piston surface (22) are arranged, which lift means is arranged to follow the reference movement of the control arm (5), and an inlet port (3) and an outlet port (4) for hydraulic medium. The body (2) encloses a pressure chamber (10) delimited by the piston surface (22) of the lift means (6), and the movement of the control arm (5) provides a flow connection between the inlet port (3) and the pressure chamber (10) in order to move the lift means (6), and the movement of the control arm (5) in the opposite direction provides a flow connection between the pressure chamber (10) and the outlet port (4) in order to move the lift means (6) in the opposite direction.