A measuring method, wherein point cloud data of a building is acquired by a laser scanner, wherein the laser scanner has an attitude detector for detecting a tilting with respect to a horizontality or a verticality, converts the point cloud data into a horizontal distance and a height or a difference of a height based on the tilting detected by the attitude detector, sets a height line at a predetermined height on a wall surface, averages a horizontal distance information of the point cloud data included in a predetermined width with the height line as a center in a height direction, further develops the horizontal distance information along the height line in a horizontal direction, and measures a horizontal cross section at the predetermined height.