To locate a fault point of a ground fault of one line at one point of a power feed line consisting of high resistance parallel two lines with the use of current, voltage data of a zero-phase terminal not on the side of a power source.

Based on a zero-phase current of each line at a zero-phase terminal T2 not on the side of a power spruce, a differential current ΔI02 of lines is calculated, a zero-phase voltage V0 is the terminal T2 is calculated, a coefficient ρ is obtained from an equation ρ=Von.ΔI02/Ion.Vo (Von is a rated zero-phase voltage and Ion is a ground fault current at the time of one line complete ground fault), and a distance (x) to a fault point from the terminal T2 is obtained according to (x)=d(1-ρ) ((d) is length of the line).