a chuck device provided with a loosening prevention mechanism , in which claws threadedly engaged with a rotary nut are moved back and force to be opened and closed by the rotation of the rotary nut provided on a body so that a tool is clamped by the claws . a receiving portion is provided to face a rear surface of the rotary nut , rolling members are provided between the receiving portion and the rotary nut , the rear surface of the rotary nut and / or a front surface of the receiving portion is formed to be slanted surfaces expanding to the outside , and surfaces on which the rolling members are moved outwardly to contact when the tool is clamped by the claws and a fastening reactive force in a thrust direction is applied to the rolling members are formed into a movement suppressing surface for suppressing movement of the contacted rolling members .