A torsion adjusting structure of a screwdriver includes an inner tube, a front micro-adjusting rod, a spring, an upper toothed block, a lower toothed block, a stop member, a compressive member, a regulating knob and an interacting member combined together, and the torsion adjusting structure is assembled in the handle of a screwdriver. To adjust the torsion of the screwdriver, an auxiliary tool is inserted in the polygonal recessed groove of the regulating knob to rotate the regulating knob having the graduation and number of a torsion value to be set by the regulating knob aligned to the position of an indication mark on the handle. Thus, the value of the torsion of a screwdriver can conveniently be regulated via the graduations and numbers on the regulating knob. Furthermore, the front micro-adjusting rod can carry out micro-adjustment of torsion.