To provide a method for plotting a ground discharge position which can improve precision for ground discharge plotting.

A plotting device 3 divides a plotting area 100 into a plurality of plotting districts 10011,..., 100mn, and a member ship function representing degree at which a plotting point belongs to the plotting districts 10011,..., 100mn is set to the plotting districts 10011,..., 100mn, respectively, and after the plotting point is calculated, each value with which the calculates plotting point belongs to the plotting districts 10011,..., 100mn is calculated, respectively, using the membership function of each plotting district, and based on each value calculated with the membership function and a weight factor of each plotting district, the coordinate obtained by correcting the calculated plotting point is taken as a new plotting point.