Abstract: The present invention is directed to a fine-mechanical adjusting device, whose one embodiment includes a body (1) having internal threads and an end surface (8). An adjusting part (4) having external threads screws to the body (1). A clamping part (5) having internal threads screws to a part of the adjusting part (4) that extends beyond the body, and it has a seating surface (9) that faces the end surface (8). In order to eliminate the longitudinal backlash of the threads and to achieve easy, stable and accurate adjustment, an O-ring (7) is placed in a groove (10) in the end surface (8), which partly protrudes from the end surface (8).