Abstract: 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 rotatably installed; and a coil spring that is set in the spindle and rotated integrally with the spindle, the treatment tool inserted from a tip of the spindle into the coil spring being gripped by an inner diameter surface of a grip portion of the coil spring, and the coil spring has an inconstant natural frequency. Preferably, the coil spring includes the grip portion in a middle region thereof, and the grip portion has a smaller inner diameter than that of other regions.