There is provided a zoom lens system including at least a first lens group GR1 having a positive refractive power, a second lens group GR2 having a negative refractive power, a third lens group GR3 having a positive refractive power, a fourth lens group GR4 having a negative refractive power, a fifth lens group GR5 having a positive refractive power, and a sixth lens group GR6 having a negative refractive power, arranged sequentially from the object side. Zoom ratio is varied by changing the distance between the adjacent lens groups. The distance, taken as DW(i-j), between the i- and j-th lens groups at the wide angle end during at-infinity imaging and that, taken as DT(i-j), between the i- and j-th lens groups at the telephoto end during at-infinity imaging meet the following conditions (1), (2), (3), (4) and (5) DW(1-2)DT(2-3) (2) DW(3-4)>DT(3-4) (3) DW(4-5)