To provide a thumb-turn device capable of improving lock reliability with a simple construction.

The thumb-turn device has a thumb-turn 2 making locking and unlocking operations of a lock device 1, a bar member 3 detachably fixing to the thumb-turn 2 by translating toward the thumb-turn 2 and prohibiting rotary operation to the thumb-turn in an engaged state and a lock operation member 4 capable of movably operating between a locking position and an unlocking position from the interior side and controlling the movement to the direction of the release with the thumb-turn 2 of the bar member 3 at the locking position, and a cam section 5 pushing the bar member 3 to the opposite direction by rotational operating the lock operation member is provided to at least either one of the thumb-turn 2 or the lock operation member 4.