A lens device includes a hollow base, a calibration ring, and a lens assembly. The hollow base includes a bottom surface and an assembly plane opposite to the bottom surface. The assembly plane has a through hole. The calibration ring includes a shaft hole, a first annular surface, and a second annular surface axially opposite to the first annular surface. An inner wall of the shaft hole has an internal thread. The shaft hole corresponds to the through hole of the hollow base. The second annular surface is fixed on the assembly plane of the hollow base via a curing adhesive layer. The lens assembly includes a lens barrel. The lens barrel has an external thread. The lens barrel is screwed to the internal thread of the calibration ring by the external thread.