Varifocus lens device

The invention provides a focal variation lens device including the bearing seat, the rotated focusing ring connected to the bearing seat, the lens room located in the focusing ring, the elastic gasket and the cover. The matched displacement guide rail and the sliding part are set between the focusing ring and the bearing seat. The sliding part can move along with the displacement guide rail to drive the focusing ring move comparing to the bearing seat. At the same time, lens room can move with the focusing ring and generates the axis displacement relative to the bearing seat. The cover is matched to the bearing seat and the elastic gasket is clapped between the cover and the focusing ring. The lens of the invention has the small size and is easy to operate, so the lens has the good imaging quality.