A lens structure includes a first barrel, a second barrel, a third barrel, a first lens module and a second lens module. The first and the second barrel respectively have a first guiding-groove and a second guiding-groove. The third barrel has a first portion and a second portion. The first and the second portion respectively have a plurality of third guiding-grooves and a plurality of fourth guiding-grooves. The first and the second guiding-groove encircle the first and the second portion, respectively. The first and the second lens module respectively have a plurality of first guiding-portions and a plurality of second guiding-portions. The first guiding-portions are disposed in sliding way in the corresponding third guiding-groove and connected in helically sliding way into the first guiding-groove. The second guiding-portions are disposed in sliding way in the corresponding fourth guiding-groove and through the second guiding-groove.