Abstract: A dental cutting tool holder which prevents the occurrence of sliding between the cutting tool and collet chuck at high-speed rotation, and prevents dislocation of the cutting tool securely, comprising a collet chuck into which a dental cutting tool is inserted detachably, and which comprises a right cylindrical section and a plurality of arc-section segments which are contiguous to the cylindrical section and divided in a circumferential direction; a rotor into which the collet chuck is inserted, and which is driven for rotation around the axis of rotation together with the collet chuck; and a clamping member which intervenes between the collet chuck and the rotor to press the respective segments inward in a radial direction by its displacement toward one end of the axis relative to the collet chuck while releasing the inward, radially pressed condition by its displacement toward the other end of the axis. The respective segments are formed with recess sections and an axially extending protrusion section.