A dental handpiece configured to rotatably drive a dental treatment tool mounted in a chuck mechanism, the dental hand piece comprising: the chuck mechanism in which the dental treatment tool is mounted so as to be attachable and detachable, wherein the chuck mechanism includes: a hollow cylindrical sleeve into which the dental treatment tool is inserted so as to be rotatably supported; a cylindrical slide member housed in the sleeve so as to be movable in an axial direction of the sleeve; a plurality of divided movable pieces (47A, 47B) disposed in the sleeve at different circumferential positions to each other, each of the plurality of divided movable pieces including an outer peripheral surface that comes into contact with an inner peripheral surface of the cylindrical slide member, and an inner peripheral surface that comes into contact with an outer peripheral surface of the dental treatment tool inserted into the sleeve, and the dental treatment tool being held between the plurality of divided movable pieces; an elastic biasing member configured to bias the cylindrical slide member forward in an insertion direction of the dental treatment tool; and a stopper unit configured to restrict forward axial movement of the plurality of divided movable pieces in the insertion direction, at least a part of the stopper unit being partially fixed to the sleeve, and wherein the outer peripheral surface of each of the plurality of divided movable pieces (47A, 47B) and the inner peripheral surface of the cylindrical slide member contact with each other via a tapered fitting portion (51, 53) having a gradient in the axial direction, the tapered fitting portion being provided on at least one of the outer peripheral surface of the plurality of divided movable pieces (47A, 47B) and the inner peripheral surface of the cylindrical slide member, wherein the divided movable pieces (47A, 47B) are moved in a radial direction by relative movement between each of the divided movable pieces (47A, 47B) and the cylindrical slide member in the axial direction, so that fixation of the dental treatment tool and release of the fixation are performed, and characterized in that the plurality of divided movable pieces (47A, 47B) are disposed in the sleeve so as to be rotatable with respect to the sleeve about an axis of the sleeve. the chuck mechanism in which the dental treatment tool is mounted so as to be attachable and detachable, wherein the chuck mechanism includes: a hollow cylindrical sleeve into which the dental treatment tool is inserted so as to be rotatably supported; a cylindrical slide member housed in the sleeve so as to be movable in an axial direction of the sleeve; a plurality of divided movable pieces (47A, 47B) disposed in the sleeve at different circumferential positions to each other, each of the plurality of divided movable pieces including an outer peripheral surface that comes into contact with an inner peripheral surface of the cylindrical slide member, and an inner peripheral surface that comes into contact with an outer peripheral surface of the dental treatment tool inserted into the sleeve, and the dental treatment tool being held between the plurality of divided movable pieces; an elastic biasing member configured to bias the cylindrical slide member forward in an insertion direction of the dental treatment tool; and a stopper unit configured to restrict forward axial movement of the plurality of divided movable pieces in the insertion direction, at least a part of the stopper unit being partially fixed to the sleeve, and a hollow cylindrical sleeve into which the dental treatment tool is inserted so as to be rotatably supported; a cylindrical slide member housed in the sleeve so as to be movable in an axial direction of the sleeve; a plurality of divided movable pieces (47A, 47B) disposed in the sleeve at different circumferential positions to each other, each of the plurality of divided movable pieces including an outer peripheral surface that comes into contact with an inner peripheral surface of the cylindrical slide member, and an inner peripheral surface that comes into contact with an outer peripheral surface of the dental treatment tool inserted into the sleeve, and the dental treatment tool being held between the plurality of divided movable pieces; an elastic biasing member configured to bias the cylindrical slide member forward in an insertion direction of the dental treatment tool; and a stopper unit configured to restrict forward axial movement of the plurality of divided movable pieces in the insertion direction, at least a part of the stopper unit being partially fixed to the sleeve, and wherein the outer peripheral surface of each of the plurality of divided movable pieces (47A, 47B) and the inner peripheral surface of the cylindrical slide member contact with each other via a tapered fitting portion (51, 53) having a gradient in the axial direction, the tapered fitting portion being provided on at least one of the outer peripheral surface of the plurality of divided movable pieces (47A, 47B) and the inner peripheral surface of the cylindrical slide member, wherein the divided movable pieces (47A, 47B) are moved in a radial direction by relative movement between each of the divided movable pieces (47A, 47B) and the cylindrical slide member in the axial direction, so that fixation of the dental treatment tool and release of the fixation are performed, and characterized in that the plurality of divided movable pieces (47A, 47B) are disposed in the sleeve so as to be rotatable with respect to the sleeve about an axis of the sleeve.