A torque-variable single-shaft rotary shaft structure with multiple frictional pairs includes a pivot shaft. A first support is secured to a pivot shaft and a second support is disposed on the pivot shaft. An adjustment wheel assembly, a frictional assembly and an elastic assembly are fitted on the pivot shaft. The adjustment wheel assembly and the frictional assembly have a first adjustment wheel and a second frictional member synchronously movable with the first support and a second adjustment wheel and a first frictional member synchronously movable with the second support. When the first and second supports are rotated, the first and second adjustment wheels are driven to contact and abut against each other so as to provide axial action forces. The frictional assembly has multiple first and second frictional members, which are alternately arranged in frictional contact with each other to form multiple frictional pairs.