To cancel the generation of electrostatic spark caused by static electricity on a joint, by providing a metallic joint on an insulating piping and by providing a grounding means for the joint for discharging the static electricity being charged in the metallic joint when a metallic joint is provided in the middle of an insulation pipe.

A grounding means for a joint is composed of fitting clips 11, 12 and a grounding/connecting line 13. Of the fitting clips 11, 12, one fitting clip 11 has a clip-shape corresponding to a shape of a section of a hexagon nut shape 6b, one face of a hexagonal surface is cut off to make a shape for being mountable from the side of a coupler 6. Moreover, hook parts 11c which are not deviated from the hexagonal nut shape 6b is formed is formed upper and lower sides, and the fitting clip 11 is fitted and fixed from the side of the hexagonal nut shape 6b. Then, a grounding line 13 is connected to an end of the fitting clip 11, and static electricity which is charged on the coupler 6 is discharged through a branching unit 22.