A lens barrel includes a barrel wall disposed about a longitudinal axis, an external thread continuously formed on the barrel wall and having a continuous crest, and two parting lines that are longitudinally formed on the external thread and that are symmetrical about the longitudinal axis. A projection of the crest of the external thread on a plane orthogonal to the longitudinal axis has a maximum diameter and a minimum diameter. A difference between the maximum and minimum diameters is between 0.04 mm and 0.18 mm. Each of the two parting lines is disposed on portions of the external thread that define the minimum diameter.