1. An apparatus for creating a three-dimensional object model comprising: a part model creation unit for creating a three-dimensional part model having junction reference data for the junction with other part models; a part storage unit in which are stored a plurality of said part models necessary for the assembly of a three-dimensional object model; and an assembly processing unit for selecting at least two part models from said part storage unit for the arrangement in a work coordinate space to junction said part models on the basis of said junction reference data, to thereby assemble said three-dimensional object model.