An exercising device includes a main body having an elongate cord and a grip, and a weight unit adjustably mounted on the cord. The weight unit includes a connecting block mounted on the cord, and a weighting block mounted on the connecting block. The connecting block has a flexible tapered mounting post and has a mounting hole. The weighting block has a tapered pressing hole pressing the mounting post. Thus, the mounting hole of the connecting block encircles the cord completely so that when the mounting post is pressed toward the cord by the pressing hole of the weighting block, the connecting block compresses the cord tightly so as to lock the weight unit on the cord of the main body.