In a trolley-wire display device, a display reference point of point-group data is set for each point on a trolley wire having a height and a displacement measured based on a reference obtained from rails. First and second points on a track center line are used to calculate a first distance, and a third distance based on the first distance and a second distance. The first point corresponds to the display reference point. The second point corresponds to each point on the trolley wire. The first distance is a distance from the first point to each second point. The second distance is a distance from a positional start point to the first point. The third distance is a distance from the start point to each second point, and is used to create display data for displaying a height and a displacement of each point on the trolley wire.