Automatic earth line detecting system for therapeutic electrostatic potential loading device

To secure grounding of a potential generator to protect a human body from danger of being electrificated by detecting leak current between each line of a commercial power source (particularly 100 volt a.c.) and an output, and connecting one line of the commercial power source judged as the grounding side with a grounding terminal. The earth line detecting system specifically designates one end of the power source 10 to be earthed, and can ensure a reliable earthing on the earth end 1a of the potential generator 1, thereby avoiding the occurrence of an electric shock on a human body.