A telescopic tube assembly having a fixing structure, including: a first tube having at a receiving end offset toward a predetermined direction to form an inward offset arc portion and an outward arc portion opposite to each other; a second tube having an inserting end, wherein an inner diameter of the first tube is greater than an outer diameter of the second tube; and a fastening structure disposed at the receiving end of the first tube, wherein the inserting end of the second tube is inserted into the first tube through the receiving end; by locking the fastening structure, the second tube is pushed against the inward offset arc portion and fixed with the first tube; by loosening the fastening structure, the second tube is released from the inward offset arc portion and is movable relative to the first tube.