The optical system disclosed in the embodiment of the invention includes first to fourth lens groups disposed along an optical axis in a direction from an object side to a sensor side and including at least one lens, respectively, wherein the first lens group and the fourth lens group have opposite refractive powers, the second lens group and the third lens group have opposite refractive powers, positions of the first and fourth lens groups are fixed, and a position of each of the second and third lens groups is movable in a direction of the optical axis, wherein the optical system having the first to fourth lens groups is operated with magnifications according to changes in at least three modes according to a movement of each of the second lens group and the third lens group, and the following equation may satisfy: TTL/EPD_Tele