Abstract: A dental hand-piece with an air turbine wherein a collet chuck holding a cutting tool spindle, a clamping member enough to clamp tapered chuck pawls of the collet chuck convergently from the outside, and further a moving element allowed to do the fine movement toward the outside owing to the centrifugal force acting thereon during the rotation of a rotary body are all together incorporated into the turbine rotary body supported by a shaft bearing inside a head casing, and which hand-piece is so designed in such manner that the fine movement of the moving element can provoke the sliding movement tending to clamp the chuck pawls between the collet chuck and the clamping member, is disclosed. In this hand-piece, the chuck pawls are automatically clamped at the time when the turbine rotary body starts to rotate, and the holding force of the collet chuck becomes greater to perform the reliable and steady holding of the cutting tool spindle the more high-speedily the rotary body rotates.