To decrease the frequency of processing for finding an overlap and to shorten the process time by making elements, classified by straight-line patterns, among component elements hierarchical and obtaining final hierarchy information from the component elements and straight-line patterns.

A straight-line pattern decision part 102 sends straight-line pattern information on component elements to an attribute decision part 103 to extract specific properties of the straight-line patterns by checking the straight-line directions. An outline generation part 203 generates outline information on the component elements and an overlap decision part 106 checks the overlap states of the respective elements. Then a straight-line pattern extraction part 107 for division extracts a straight-line pattern for area division by referring to the overlaps of arbitrary attributes and a length rate comparison part 110 compares the length rates of the straight-line patterns; and an object area division part 112 further divides the object area and an object area selection part 113 makes a choice. Lastly, a hierarchy integration part 115 integrates hierarchy information on the component elements and information on the straight-line pattern for division.