A BOM is merged to a BOM stored in a BOM data base by means of the component identification judgment means that compares the product record in the BOM file with the product listed in the BOM stored in the BOM data base and makes judgment conformity between these two product records and a BOM rearrangement means that has a BOM rearrangement means a coding rule estimating means determining the coding compliance. A component assembly flag and a component assembly status flag are appended to the BOM stored in the BOM data base so that the expansion to the lower hierarchal layers of the component is presented.