The invention relates to an expensive zoom lens that has a zoom ratio of as high as about 5 and high optical performance and is very thin in its depth direction. With the invention, the optical path of the optical system is easily bendable by means of a reflecting optical member. The zoom lens includes a first lens group G1 having positive power, a second lens group G2 having negative power, a third lens group G3 having positive power and a fourth lens group G4 having positive power, and comprises five lens groups in all. The first lens group G1 comprises, in order from its object side, a lens component of negative refracting power, an optical path-bending reflecting optical member P and a lens component of positive refracting power. Upon zooming from the wide-angle end to the telephoto end, the first lens group remains substantially fixed with respect to an image plane I, the second lens group G2 moves only toward the image side, and the fourth lens group G4 moves in such a way as to be positioned nearer to the object side at the telephoto end than at the wide-angle end.