System (1) for diagnosing the balance of a user or patient, comprising a platform (2, 21), a U-shaped support structure (3) and at least three linear actuators (A1, A2, A3) characterized in that the U-shaped support structure (3) partially surrounds the sensor-equipped platform (2) allowing a user access to said platform (2), and in that said structure has guiding elements (70) for guiding the mobile ends (211, 221, 231) of said actuators that allow the vertical displacement of said mobile ends with respect to the structure (3), said mobile ends (211, 221, 231) being mechanically connected to the platform (2, 21) such that when said mobile ends (211, 221, 231) are vertically displaced, they cause the movement of the platform (2, 21).