PURPOSE: To improve a picture used by a computer tomographic device, etc., by utilizing capillarity to admit an adhesive to the groove of an insulating plate, improving operativity and eliminating irregularity of the coating amount of the adhesive, and eliminating the disorder of a signal current, etc.

CONSTITUTION: An adhesive injection hole 6 communicating with the grooves 11 of the insulating plate 1 is formed in at least either one of both lengthwise end surfaces 12 and 13, i.e. 12. Then, an adequate amount of adhesives 3 are injected into an injection hole 6 by using an injector 7, etc., after the insulating plate 2 is inserted into between a couple of facing grooves 11. Then, the adhesives 3 are liquid until they are cured, so they stay in the injection hole 6, then move to the grooves 11 by capillarity to reach the other surface 13 through the gap between the grooves and an electrode plate 2. A water absorbing material such as sponge 5 is placed on the other surface 13 to absorb excessive adhesives 3.