PURPOSE: To simply measure grounding resistance without using any auxiliary grounding rod by connecting unknown and known grounding parts of grounding resistance with a lead wire and applying current of a frequency capable of discriminating a commercial frequency through a clip type transformer.

CONSTITUTION: Grounding resistance R of a grounding part 11 of a distribution line 10 is known and other grounding resistance Rx of another grounding part 21 of an independent telephone line 20 is unknown. And the grounding parts 11, 21 are connected with a lead wire 30, which is clipped with a clip type transformer 40. Current of a frequency capable of clearly discriminating a commercial frequency on the ground through the grounding parts 11, 21 is applied with one transformer 41 for constituting the transformer 40 from the lead wire 30. The applied current indicates a value inversely proportional to a resultant value composed of the grounding resistance R of the grounding part 11 and the grounding resistance Rx of the grounding part 21. Such applied current is detected with the transformer 41 and the detection value includes information of (R+Rx). Accordingly, operation is performed with a measuring device body 50 from the detection value for the purpose of measuring the value of the grounding resistance Rx.