A surveying data processing device comprising a processor or circuitry, the processor or circuitry configured to: acquire first point cloud data and second point cloud data, the first point cloud data being obtained by performing laser scanning, from a first viewpoint, on an object to be measured, the second point cloud data being obtained by performing laser scanning, from a second viewpoint, on the object to be measured; acquire data of a three-dimensional model of the object to be measured, this data being prepared in advance; obtain a correspondence relationship between the first point cloud data and at least a part of the three-dimensional model; characterised in that the processor or circuitry is further configured to: integrate information of the at least a part of the three-dimensional model with the first point cloud data to generate extended data in which the first point cloud data is extended, on a basis of the correspondence relationship between the first point cloud data and the at least a part of the three-dimensional model; and determine a correspondence relationship between the extended data and the second point cloud data, wherein the three-dimensional model contains an occluded part of the object to be measured that is hidden and is thus not viewable from the first viewpoint but is viewable from the second viewpoint, and the determination of the correspondence relationship between the extended data and the second point cloud data includes determining a correspondence relationship between the occluded part and the second point cloud data. acquire first point cloud data and second point cloud data, the first point cloud data being obtained by performing laser scanning, from a first viewpoint, on an object to be measured, the second point cloud data being obtained by performing laser scanning, from a second viewpoint, on the object to be measured; acquire data of a three-dimensional model of the object to be measured, this data being prepared in advance; obtain a correspondence relationship between the first point cloud data and at least a part of the three-dimensional model; characterised in that the processor or circuitry is further configured to: integrate information of the at least a part of the three-dimensional model with the first point cloud data to generate extended data in which the first point cloud data is extended, on a basis of the correspondence relationship between the first point cloud data and the at least a part of the three-dimensional model; and determine a correspondence relationship between the extended data and the second point cloud data, integrate information of the at least a part of the three-dimensional model with the first point cloud data to generate extended data in which the first point cloud data is extended, on a basis of the correspondence relationship between the first point cloud data and the at least a part of the three-dimensional model; and determine a correspondence relationship between the extended data and the second point cloud data, wherein the three-dimensional model contains an occluded part of the object to be measured that is hidden and is thus not viewable from the first viewpoint but is viewable from the second viewpoint, and the determination of the correspondence relationship between the extended data and the second point cloud data includes determining a correspondence relationship between the occluded part and the second point cloud data.