PURPOSE: To drastically reduce the cost of a zoom lens barrel by providing a guide bar and a feed screw which has plural feed screw tooth flanks formed in a fixed lens barrel, and applying a rotary driving force from a driving source to the feed screw and moving plural moving frames in the direction of the optical axis.

CONSTITUTION: For example, when a zoom driving command for zooming from a wide-angle side to a telephoto side is supplied, a driven gear 20 is driven to rotate and its turning force is transmitted to the feed screw 16 through a small gear 21. Then a 1st driven projection 13 and a 2nd driven projection 18 formed on a 2nd moving frame 12 and a 3rd moving frame 17 which are restrained by the guide bar 11 from rotating are driven to move a 2nd group lens 2 backward, and a 3rd lens 3 moves forward simultaneously. Consequently, the optical axis positions of respective lens groups are controlled by one feed screw (lead screw) 16, so the cost is reduced greatly.