A measuring apparatus (10) comprises a transducer (11) for measuring preload and torque of a screw. The transducer in turn comprises a first and second sensor element formed by two axially spaced annular zones (16, 17) of a hollow body (15) which are provided with respective load-cell sensors (18, 19). The two zones are separated by an annular zone (20) of the hollow body with a wall with a greater thickness and in which internally there is provided a non-rotating coupling seat (21) with the threaded-hole element (22) in a part of which the screw is tightened.