To effectively suppress drying of a stamp material provided with a torque wrench without impairing workability and stamp performance.

In a stamp part for the torque wrench performing a marking when fastening force to a bolt or a nut reaches a prescribed value, the stamp material 4 which is supplied with ink and has a front end made as a stamp surface 4b is provided. The stamp material 4 is made of a porous body into which ink penetrates, and has a surface layer except an ink supplied surface and the stamp surface 4b which is made of a hard-to-penetrate material 5. Suitably, the hard-to-penetrate material 5 is made to have a hard-to-penetrate property by selectively changing the surface in quality by performing heat treatment for the stamp material 4. Ink drying in the stamp part can be suppressed without impairing stamp performance, generation of a secular marking defective can be prevented and marking quality can be stabilized.