There is provided a conductive hollow tube (3) which is brought into tight contact with the top surface of a grounding conductor (1a) at a position where a first end having an opening plane (4a) with an inner diameter matching a diameter of a hole (2a) formed on the grounding conductor (1) overlaps with the hole (2a), and which is bent so that an opening plane (4b) of a second end faces the top surface direction and that an intermediate portion between the first end and the second end is arranged parallel to the grounding conductor (1), and a conductive liquid supplied from the opening plane (4a) of the first end is passed through the conductive hollow tube (3) and discharged to the outside from the opening plane (4b) of the second end.
