In order to define parts in shipbuilding, we need a lot of information which are plate thickness, shapes of grooves, shapes of slots and so on. It is needless to say that ship structure consists from so many parts that the work to generate information of parts is one of the most hard works in shipbuilding industry. In order to support the work to define parts, the authors have developed system for parts design, by using our previous system which is the prototype system of CIM for shipbuilding, we call it SODAS (System Of Design and Assembling for Shipbuilding). In this paper, we have proposed a new concept. It is “Superiority and Inferiority of parts” for description of a relation between two parts. The information is inputted into parts as attribute data. Because of recognition of relation between parts by this information at design stage, we can design a detail shape of parts.