An object of the present disclosure is, in performing three-dimensionalization of an object point cloud by a laser or a radar, to reduce an amount of calculation in the axial direction of three-dimensional space coordinates, into which the object point cloud is to be mapped, while increasing accuracy in the three-dimensionalization of the object point cloud. The present disclosure calculates an absolute value of a difference between vehicle attitude data with a high sampling frequency and vehicle attitude data with a low sampling frequency. When the absolute value of the difference is small, the vehicle attitude data with the high sampling frequency is decimated and the vehicle attitude data with the low sampling frequency is outputted, to thereby reduce the amount of calculation in the axial direction of the three-dimensional space coordinates, into which the object point cloud is to be mapped. On the other hand, when the absolute value of the difference is large, the vehicle attitude data with the high sampling frequency is outputted to increase the accuracy in the three-dimensionalization of the object point cloud. Finally, the object point cloud is three-dimensionalized based on the data of vehicle attitude and data of the object point cloud.