Disclosed is a coupling device capable of remarkably reducing time for a reinforcing bar coupling work and reinforcing compression strength and bending strength of reinforcing bars while totally fixing the reinforcing bars by pressing a cone member having curved sides with hydraulic pressure in the vertical direction to the reinforcing bar. The present invention can stably transmit power from the cone member to a reinforcing bar fixing member through an external power dispersion medium member so that it can effectively prevent the displacement of the reinforcing bar and the loose connection of the reinforcing bars.
