The front fork of a bicycle, as shown in FIG. 1, is generally comprised of a blade holder 10 for connection to the bicycle's head tube, two tubular upper fork blades 20 bilaterally and fixedly connected to two fork blade coupling portions 11 of the blade holder 10 at the bottom and each having a bellows tube 21 at the bottom, and two tubular lower fork blades 30 respectively connected to the bellows tube 21 of either tubular upper fork blades 20 at the bottom. Inside the bellows tube 21, a shock absorbing device is installed to absorb shocks transmitted from the front fork. Various hydraulic and pneumatic shock absorbing devices as well as shock absorbing springs have been disclosed for this purpose. These shock absorbing devices are commonly heavy and/or complicated in the structure. Therefore, the installation of a conventional shock absorbing device significantly increases the weight of the front fork of the bicycle.