The design/manufacture support system has a self company/correspondent parts number correspondence storing unit for storing the correspondence between parts numbers of self company and correspondent parts, a self company parts bill storage unit for storing a structure of parts of a self company product, a correspondent parts bill storage unit for storing a structure of parts purchased from a correspondent, a representative part creation unit for creating a representative part from the correspondence between self company and correspondent parts numbers stored in the self company/correspondent parts number correspondence storing unit, and a parts bill creation unit for creating a parts bill from the representative part created by the representative part creation unit, the self company parts bill stored in the self company parts bill storage unit and the correspondent parts bill stored in the correspondent parts bill storage unit.