To make possible using three-dimensional data of electric cable housing components to automatically generate and output a drawing that is simple and useful as two-dimensional data for clearly representing the relationship between upper and lower components. Determination controller 121 of two-dimensional data generation unit 120 converts three-dimensional data of electric cable housing components, which is read by the data reading part 122, into a line segment for each component by diagram generation part 123, and converts a contact part between components or a part where components partially overlap with each other, into an intersection point, to generate a diagram composed of the line segment and intersection point. Determination controller 121, by coplanarization part 125, shifts line segments of a plurality of components that overlap vertically on the diagram onto a single plane, and slides the line segments at a predetermined interval to represent the vertical overlap on the plane. Determination controller 121 outputs the generated two-dimensional data of the electric cable housing components from interface unit 110 in the form of file by file output part 127, and stores the data in the form of file in storage unit 130.