An antitheft device (1) to be attached to an item capable of being stolen and including a control portion (2) that is rotatable relative to an attaching portion (3), the attaching portion (3) including an attaching element (4) that is translatably movable with an unlocked position, for placing of the item into the device (1) and for removing same, and wherein the rotation of the control portion (2) relative to the attaching portion (3) translates the attaching element (4), and with a locked position for maintaining the device (1) on the item and wherein the rotation of the control portion (2) relative to the attaching part (3) does not translate the attaching element (4). The control portion (2) includes a transmission mechanism (15) with a controller for the torque applied to the control portion so that the locked position is achieved for a predetermined value of the torque of forces.