A lens device includes a lens barrel and a first lens. The lens barrel includes an object-side end. The first lens is fixed to the object-side end of the lens barrel, is configured to form an optical axis, and includes a minor diameter portion near an object side of the lens device and a major diameter portion near an image side of the lens device. The major diameter portion is connected to the minor diameter portion. A section of the first lens sectioned along the optical axis is higher at a middle portion than at both side portions. The first lens is protruded at the middle portion towards the object side to form a pillar with respect to the both side portions thereof.