A device for gripping a treatment tool of a handpiece is provided that can firmly grip the treatment tool and achieve a high vibration absorbing property.The device for gripping a treatment tool of a handpiece includes: a spindle 18 rotatably installed and a coil spring 28 that is set in the spindle 18 and rotated integrally with the spindle 18, the treatment tool inserted from a tip of the spindle 18 into the coil spring 28 being gripped by an inner diameter surface of a grip portion of the coil spring 28, and the coil spring 28 has an inconstant natural frequency. Preferably, the coil spring 28 includes the grip portion 281 in a middle region thereof, and the grip portion 281 has a smaller inner diameter than that of other regions.
