A zoom lens of rear focus type in which a total lens system is able to be miniaturized by further miniaturizing a prism, without deteriorating an optical performance. The zoom lens has a first lens group (GR1) to a fifth lens group (GR5) having refraction powers of a positive, negative, positive, positive and negative from the object side in this order, respectively, and is configured to carry out a zooming operation by moving the second lens group (GR2) and the fourth lens group (GR4). In addition, the first lens group has a front-side lens group having an negative refracting power, an optical element for folding an optical path, and a backside lens group having a positive refracting power, from the object side in this order, and further a condition of 1.3<.beta.5<2.2 is satisfied, provided that an imaging magnification of the fifth lens group (GR5) at where an object distance is at infinity is .beta.5. Therefore, the focal length of the lens groups positioned closer to the object is shortened and an effective diameter of the first lens group (GR1) can be made small, whereby it is possible to make the optical element (for example, prism P1) thinner.