An impact torque adjusting device of a hydraulic torque wrench, said impact torque adjusting device comprising: a liner having a liner lid (7a; 7b) and a fluid path (7c; 7d) formed in said liner lid, which liner is rotated by a rotor; a main shaft disposed inside of the liner, said main shaft having a blade insertion part and having two directions of rotation; and blades provided in said blade insertion part; wherein the inside of the liner comprises a high-pressure chamber and a low-pressure chamber in operation; said high-pressure chamber communicates with said blade insertion part; a working fluid path communicates with the inside of said liner; a valve body is disposed in the working fluid path and biased in a direction of opening the working fluid path; the rear back side of the valve body is provided with an oil chamber communicating with said blade insertion part of the main shaft by way of said fluid path formed in said liner lid (7a; 7b); and the valve body is arranged such that the working fluid path is narrowed in response to an elevation of the pressure of the working fluid in the blade insertion part of the main shaft along with an elevation of the pressure of the working fluid in the high-pressure chamber in both of the two directions of rotation of said main shaft. a liner having a liner lid (7a; 7b) and a fluid path (7c; 7d) formed in said liner lid, which liner is rotated by a rotor; a main shaft disposed inside of the liner, said main shaft having a blade insertion part and having two directions of rotation; and blades provided in said blade insertion part; wherein the inside of the liner comprises a high-pressure chamber and a low-pressure chamber in operation; said high-pressure chamber communicates with said blade insertion part; a working fluid path communicates with the inside of said liner; a valve body is disposed in the working fluid path and biased in a direction of opening the working fluid path; the rear back side of the valve body is provided with an oil chamber communicating with said blade insertion part of the main shaft by way of said fluid path formed in said liner lid (7a; 7b); and the valve body is arranged such that the working fluid path is narrowed in response to an elevation of the pressure of the working fluid in the blade insertion part of the main shaft along with an elevation of the pressure of the working fluid in the high-pressure chamber in both of the two directions of rotation of said main shaft. the inside of the liner comprises a high-pressure chamber and a low-pressure chamber in operation; said high-pressure chamber communicates with said blade insertion part; a working fluid path communicates with the inside of said liner; a valve body is disposed in the working fluid path and biased in a direction of opening the working fluid path; the rear back side of the valve body is provided with an oil chamber communicating with said blade insertion part of the main shaft by way of said fluid path formed in said liner lid (7a; 7b); and the valve body is arranged such that the working fluid path is narrowed in response to an elevation of the pressure of the working fluid in the blade insertion part of the main shaft along with an elevation of the pressure of the working fluid in the high-pressure chamber in both of the two directions of rotation of said main shaft.