Abstract: A joint structure effective in reducing return loss and insertion loss of signals includes a body, a sleeve, a resilient element, a metallic pipe, a rod, two washers, and a packing. The sleeve is disposed in the body and penetrable by a terminal line. The sleeve has a positioning ring circumferentially in tight contact with the body and receives the resilient element. The circumference of the resilient element is integrally formed as a unitary unit and has longitudinal slashes whose ends are provided with bumps, respectively. A positioning ring is disposed at the other end of the resilient element. The resilient element and the rod are insertable into two ends of the metallic pipe, respectively. The rod has an end for penetrating the washers and packing, and has a positioning ring for enabling engagement and positioning of the washers, the packing, the rod, and the metallic pipe.