The present invention refers to a device for tensioning a connecting element fastened to a component to be tightened, comprising a fixation element for holding the connecting element; a support element for supporting the device against the component; and an actuating unit with a fluid chamber for receiving a fluid and a piston which is translationally guided in the fixation element. The actuating unit is configured for manipulating a volume of the fluid chamber by translationally actuating the piston so as to move the fixation element relative to the support element. The piston is coupled to the fixation element by means of at least one ball or roller screw.