Abstract: A tool holder of the hollow taper shank in a tool machine is disclosed. A resisting block supported by a spring is received within a tool holder. As the short knife is disposed within the tool holder, the elastic force of the spring can be overcome. At first, a plurality of steel balls and a resisting block are pushed inversely until the front edge of an wider portion of the short knife passes through the steel ball. Now, the spring will release the energy from elastic deformation so as to enforce the resisting block to move forwards and outwards so as to return to the original position. Thereby, the knife can be firmly secured.