Target point cloud data about a specific road are extracted from perimeter point cloud data acquired by moving a road surface measurement device along a measurement route and scanning the surroundings thereof. A data storage unit stores trajectory point sequence data that represent, as a plurality of trajectory points, the perimeter point cloud data and a trajectory of the movement of the road surface measurement device. A trajectory point sequence setting unit acquires a trajectory point sequence at equal intervals from the trajectory point sequence data. An extraction area setting unit sets, as extraction areas, a column area Ci and a parallelepiped area Hi that are geometric areas disposed at predetermined positions below a trajectory point Xi. An approximate nearest neighbor search processing unit and an extraction processing unit extract, as the target point cloud data, point data that belong to this extraction area of the perimeter point cloud data.