In recent years， with progress of an electric information society，investigation about earthing for detached house have been needed from the viewpoint of safety of information and communication equipment for lightning. In this paper，a new earthing system using reinforcing bars in a house foundation was proposed.The reduction effect for lightning overvoltage，frequency characteristic of concrete impedance，inf1uence on operation of earth leakage breaker for leakage current and secular change in earth resistance of the earthing system were investigated experimentally. The overvoltage for consumer equipment due to lightning could be suppressed in the earthing system in case that the system was applied to an actual house. The impedance of concrete in the earthing system was 190 Ω for 50 Hz and less or equal 40 Ω for over 100 kHz. These values are sufficiently low as the impedance for safety for electrical leak and electric shock. It was confirmed that the earth leakage breaker could operate with the earthing system. The maximum value of the earth resistance was measured to be 180 Ω.As a result，it can be said that the system proposed by us is effective as the earthing system.