PURPOSE: To prevent colliding of a hanging member with a supporting arm at the time a supporting insulator is shaked, to reduce the buckling stress of a supporting member and to prevent the bending stress from being generated at the hanging member.

CONSTITUTION: A supporting insulator 15 is rockingly hung and supported to the supporting arm 11 of a steel tower via a link 29. A supporting member 31 is rotatably mounted at the lower end of the link 29. The member 31 is disposed to be extended horizontally from the end of the arm 11 via a hanging member 32 between the upper end of the like 29 and the member 31. An arrester insulator 19 is mounted at the end of the member 31. When the insulator 15 and the insulator 19 are shaked, the coupling part 33 of the member 32 to the member 31 is disposed near the base end of the member 31 so that the member 32 does not collide with the arm 11.