There are saved layout data which have parent cell information indicative of higher order cell data to directly refer to low order cell data (or basic element data), thereby defining a reverse hierarchical structure. More specifically, both of basic element data (figD1 and figD2) have cell data (cell2) as the parent cell information, all of basic element data (figD3 to figD5) have cell data (cell3) as the parent cell information, the cell data (cell3) have two identical cell data (cell2 and cell2) as the parent cell information, and the cell data (cell2) have three identical cell data (cell3, cell3 and cell3) as the parent cell information.