To solve the problem that there are many cases that a desired ground resistance value cannot be obtained since a rod like ground body constituting a conventional ground device has a small contact area with earth and accordingly earth resistivity of an installation place is high.

Since a ground conductor is wound around spirally in a region embedded and installed in a vertical hole excavated in the earth of a nonconductive support body, the contact area of the ground conductor and the earth can be made large and accordingly the desired ground resistance value can be obtained.