In an adjusting knob mechanism, a base includes a first supporting portion and a second supporting portion. A first clicking gear includes a plurality of first indentations and disposed on the first supporting portion. A second clicking gear includes a plurality of second indentations and disposed on the second supporting portion. A limiting element is disposed on the base. A movable element is disposed within the limiting element and configured to move in an axial direction of the base relative to the limiting element. A connecting mechanism extends into the limiting element. An adjusting cover is connected to the movable element by the connecting mechanism, so as to move the movable element in the axial direction of the base relative to the limiting element and the second clicking gear. The adjusting cover is configured to rotate the limiting element and the movable element through the connecting mechanism.