A lens device includes a first barrel surrounding an optical axis, a first frame coupled rotatably to the first barrel and surrounding a first axis, and an adjusting unit. The adjusting unit has an adjusting groove formed in one of the first barrel and the first frame, and having adjusting groove segments, one of which extends spirally. The adjusting unit further has adjusting blocks formed on the other one of the first barrel and the first frame and engaging respectively and slidably the adjusting grooves. The first frame is rotatable relative to the first barrel to adjust the first axis relative to the optical axis.