is installed in the electrode mounting part 87 the both end portions of the upper holder 81 are combined being inserted in the insertion groove 88 of the lower holder 80 the upper surface of the inner holder 83 is abutted to the upper mounting groove 81 b formed on the lower surface of the upper holder 81 under the above condition the fixing pin 84 is inserted in the pin hole 85 a at the rear of the main wall part 85 of the lower holder 80 and the fixing pin is combined thus to pass through the pin hole 81 a of the upper holder and the pin hole 86 a formed in the protrusion part 86 of the lower holder when the stopping groove 84 a formed in the fixing pin 84 passes the upper side of the vertical hole 89 a the stopper ball 91 supported upwards by the electricity of the spring 90 is inserted in the stopping groove 84 a of the fixing pin 84 in case the electrode structure in accordance with the present invention assembled as above is dismantled the assembling process is performed in the reverse order namely when the user pulls the fixing pin 84 to the opposite direction that it is inserted the stopper ball 91 inserted in the stopping groove 84.