A fastening structure for fastening a member to the rim of the steering wheel of a motor vehicle is disclosed to include a mounting base frame, which has two mounting holes at two distal ends for the mounting of an external member and two sets of hooks bilaterally protruded from the top wall between the mounting holes, and two elastic fastening belts, which have a hook hole one each of the respective two distal ends respectively hooked on the hooks at the mounting base frame to secure the mounting base frame to the rim of the steering wheel of the motor vehicle firmly in place.