Disclosed is a video-camera imaging-system lens barrel which overcomes the problem of a four-lens-group-type video-camera imaging-system lens barrel, which has a complicated structure and large size and weight due to the large number of lens groups. In a so-called two-group-type lens system, a first lens group 2 and a second lens group 3, which are in focus in an imaging plane (CCD 4) for each zoom magnification at fixed subject distances .alpha.m and .beta.m, are controlled such that they move along zoom tracking curves 1.sub.1, 1.sub.2, 1.sub.3 and 1.sub.4 which represent the paths of movement of the respective positions of the first lens group and the second lens group.