A rotating shaft mechanism includes a first connecting portion, a second connecting portion, a central shaft rotatably connected to the first connecting portion and the second connecting portion, and an adjusting unit disposed on the central shaft. The adjusting unit includes an adjusting ring disposed around the central shaft, a first washer disposed around the central shaft and configured to generate a force to the first connecting portion or the second connecting portion. A position of the adjusting ring with respect to the central shaft is axially adjustable for adjusting the force so that the first connecting portion or the second connecting portion is rotatable or fixed relative to the central shaft.