An adjustment device for adjusting seats includes a rotatable drive element, a rotatable output element, a first clamping element freewheel that blocks the output element continuously in different positions in both adjustment directions and that is released by a release element and a second clamping element freewheel that is coupled via the release element to the first clamping element freewheel, blocks the output element continuously in different positions in both adjustment directions and is released by an actuating element. The drive element is pre-tensioned in a middle position via two springs acting in different directions and the two springs pre-tension the actuating element in a middle position.