The invention relates to a device for clamping a hollow shaft tool (1) or tool holder provided with a conical hollow shaft (3) in a machine spindle (2) provided with a taper bore (4), especially for use in a machine tool. The device comprises a clamping sleeve (7), axially displaceable inside the machine spindle (2), a tow-rod (8) for displacing the clamping sleeve (7) and being movable between a release position and a clamping position, and a plurality of pincer elements (19) associated with the clamping sleeve (7). The pincer elements are radially displaced by the displacement of the clamping sleeve (7) and have clamping faces (21, 24) to be placed on a conical inner surface (22) of the conical hollow shaft (3) and an opposite surface (26) on the work spindle (1). The aim of the invention is to provide a clamping device of the aforementioned kind wherein the hollow shaft tool is reliably retained in the machine spindle even when the tow-bar is already released. For this purpose, the clamping sleeve (7) can be axially displaced relative to the tow-bar (8) and is axially biased by a compression spring (14) against the motion of release of the tow-bar (8).