PURPOSE: To obtain the variable power lens which changes the magnification while keeping the distance between the object face and the image forming face fixed and can be applied to an optical system having a wide power range and has various aberrations satisfactorily corrected by satisfying a specific condition.

CONSTITUTION: This variable power lens satisfies the condition -3.0<f3.4/f<-1.0 where f3.4 is the resultant focal length of third and fourth lenses L3 and L4 and (f) is the focal length of the whole of the lens system for unmagnification. The overall length of the variable power lens is shortest at the time of unmagnification. At the time of varying the power, a second lens group Gr2 and a fourth lens group Gr4 are moved in the same direction while keeping the interval between these lenses constant to change the projection magnification while keeping the distance between the object face and the image forming face constant. By this constitution, the second lens group Gr2 and the fourth lens group Gr4 can be held by an integrated lens holding member.