The invention discloses a lens adjusting device including a base, two dead levers, a sliding seat, a first gear train and a second gear train. The two dead levers are respectively fixed on two sides of the base. The sliding seat is arranged on the two parallel dead levers in the first axial direction in a sliding manner. A lens is fixed on the sliding seat, and a tooth row is arranged on one side of the sliding seat. The first gear train is provided with a first gear and a coaxial worm, wherein the first gear is sleeved on one of the dead levers, so that the first gear and the worm can rotate relative to the dead lever. The second gear train is arranged between the dead lever and the tooth row. The second gear train is provided with a worm wheel and a coaxial second gear, wherein the worm is used for driving the worm wheel, and the second gear is used for driving the tooth row, so that the sliding seat can move relative to the two dead levers.