A chuck device includes: a chuck body having a tapered hole at a front end portion and being fixed to a rotational spindle of the machine tool; a collet capable of being reduced in diameter and inserted into the tapered hole for holding the tool; and a nut that can be screwed to the chuck body for fastening the collet. A non-alignment prevention member is provided for suppressing relative movement by bringing the nut into radial contact with the chuck body even when the spindle of the machine tool is rotated and includes a first nut rear end side tapered surface at a farther rear end side than a screw portion, and a chuck body side tapered surface formed in the chuck body for coming into contact with the first nut rear end side tapered surface when the nut is screwed up.