The invention provides a zoom optical system and a shooting device. The zoom optical system realizes small size, low cost, relatively low F value, good chrominance correction and high optical performance. The zoom optical system successively comprises, from the object side, a positive first lens group (G1) which is fixed during the zooming, a second lens group (G2) which is moved along an optical axis so as to perform the zooming, a diaphragm which is fixed during the zooming, a positive third lens group (G3) which is fixed during the zooming, and a positive fourth lens group (G4) which corrects the image plane position and focuses along with the zooming operation. The second lens group (G2) successively comprises, from the object side, a negative lens, a positive meniscus lens with a concave surface being oriented to the object side, a biconcave lens and a positive lens. The zoom optical system is configured in such a manner to satisfy the prescribed conditions related to the focal length of the second lens group (G2), the Abbe number of the positive meniscus lens of the second lens group (G2) and the amount of movement of the second lens group (G2) during the zooming from the wide end to the tele end.