PURPOSE: To surely confirm the gripping of a tool holder without erroneous detection and to make a tool holder gripping device lightweight by using a reinforced synthetic resin mold article for a grip, by controlling the operation range of the grip with the use of a positioning member and by embedding a detecting pin in the rear end part of the grip in order to confirm the operating condition of the grip.

CONSTITUTION: A pair of right and left reinforced synthetic resin mold grips 1, 1 one of which is embedded in its rear end part, with a detecting pin 5 for confirming the gripping of a tool holder, and between which a tool holder positioning key 2 and a resilient member 4 are set on a support plate 10 so that they may be operated by means of a fulcrum shaft 6. Grip positioning pins 3, 3 are provided on an operating plane for the grips 1 with reference to the support shaft 6 so as to prevent the grips 1, 1 from being operated simultaneously in one direction, and the position of the detecting pin 5 for confirming the gripping of the tool holder is detected by a detector 7 so as to confirm the gripping of the tool holder 11.