A trolley-wire measurement device comprising: a rail detection unit to detect rails from point-group data that is an aggregate of points obtained by measuring a target object three-dimensionally, the rails defining a railway on which a train runs; a reference setting unit to set a reference for measuring a height and a displacement of a point on a trolley wire on a basis of the rails detected from the point-group data in the rail detection unit; a trolley-wire detection unit to detect the point on the trolley wire from the point-group data ; a height and displacement measurement unit to measure the height and the displacement of the point on the trolley wire by using the reference; and a data input unit to obtain latest point-group data from a measuring device configured to measure the target object three-dimensionally, wherein the rail detection unit is configured to detect the rails by using the latest point-group data obtained, and updates a rail position, the reference setting unit is configured to set the reference for measuring the height and the displacement of the point on the trolley wire on a basis of rails detected from the latest point-group data and previous point-group data, the trolley-wire detection unit is configured to detect the point on the trolley wire from the latest point-group data obtained, and the height and displacement measurement unit is configured to measure the height and the displacement of the point on the trolley wire detected from the latest point-group data, by using the reference set on the basis of the rails detected from the latest point-group data and the previous point-group data. a rail detection unit to detect rails from point-group data that is an aggregate of points obtained by measuring a target object three-dimensionally, the rails defining a railway on which a train runs; a reference setting unit to set a reference for measuring a height and a displacement of a point on a trolley wire on a basis of the rails detected from the point-group data in the rail detection unit; a trolley-wire detection unit to detect the point on the trolley wire from the point-group data ; a height and displacement measurement unit to measure the height and the displacement of the point on the trolley wire by using the reference; and a data input unit to obtain latest point-group data from a measuring device configured to measure the target object three-dimensionally, wherein the rail detection unit is configured to detect the rails by using the latest point-group data obtained, and updates a rail position, the reference setting unit is configured to set the reference for measuring the height and the displacement of the point on the trolley wire on a basis of rails detected from the latest point-group data and previous point-group data, the trolley-wire detection unit is configured to detect the point on the trolley wire from the latest point-group data obtained, and the height and displacement measurement unit is configured to measure the height and the displacement of the point on the trolley wire detected from the latest point-group data, by using the reference set on the basis of the rails detected from the latest point-group data and the previous point-group data. <EOS>