The invention relates to a tool holder comprising a tool box which is provided with a tool seat for receiving a tool in such a manner that it can be replaced. The tool seat is configured as a bore and comprises a tool insertion opening. The tool holder has a fastening side with a fastening part and, facing away from said fastening side, an exterior, and during use of the tool centrifugal forces are effective in the direction from the fastening side to the exterior. The aim of the invention is to ensure the free rotability of a tool inserted in the tool holder of the aforementioned kind even if gangue material enters the tool seat. For this purpose, the holding part is provided with an opening penetrating the inner wall of the tool seat and creating a spatial connection to the exterior, and the opening opens the tool seat towards the exterior.