In manufacturing management that faces to small size and wide variety production, it is difficult to know appropriate cost estimation of family products. Family products, which is an abstract production items having several options of parts and production processes, need to be described by bill of manufacturing (BOM) information efficiently because the information volume increases exponentially. This paper proposes a method to describe BOM structure for family products, and then shows an example of calculation of these family product costs by using production records of the previous period. Finally, the future plan to apply the method to an actual manufacturer is briefly discussed.