An apparatus for generating assembly steps and an assembly sequence for sequentially assembling a product is provided with: a part detecting section for detecting designated characteristic shapes from the 3D CAD model, detecting a part present in a radial direction of each characteristic shape, and detecting a part present in an axial direction of the detected part; a section for generating a directed graph where a node denotes a part and a directed edge denotes a connection precedence relationship between parts; an assembly graph generating section for generating, an assembly graph where a node denotes a part and an edge denotes an adjacency relationship; a work order adding section for adding work contents and work orders to a list of the detected unconnected parts; and a generating section for generating the assembly sequence and an assembly direction by generating and reversely converting a disassemblable direction and a disassembly sequence.