PURPOSE: To perform the calculation of the amount of earth automatically by preparing the data for a cross-section diagram or longitudinal section diagram at each surveying point based on the input data of a topographical data read out means, designing elements, and the earthwork conditions.

CONSTITUTION: The data inputted as initial data from a coordinate reader 1 and input keys 2 and 3 are stored in a memory unit 6 via an imput control circuit 4 and an operational circuit 5. The operating circuit 5 calculates the cross section diagram data at each surveying point based on the data stored in the memory unit 6, and the result is stored in a memory unit 7. An operating circuit 8 which is different from the operating circuit 5 obtaines the area of a slope face based on the cross section data stored in the memory unit 7 for each surveying point, and calculates the amount of the earth to be cut and filled from the obtained slope face area. The result is stored in the memory unit 7. An output control circuit 9 outputs the various data stored in the memory unit 7 to a CRT control circuit 10 or a plotter control circuit 11. Then the cross section, the slope face area, the amount of the earth, and the like are dispalyed.