There is a growing need for top-down design methodology for a discrete event system. In top-down design of the discrete event system, we begin with a high-level model of the system and refine it step-wisely until a sufficiently low-level model is obtained. In the previous researches, most of the proposed refinement technique has been a "transition-based technique", which replaces each transition with subnet. However, in case of assembly Petri net, each place has useful informations for the refinement rather than each transition. This means that a "place-based refinement technique", is needed for assembly Petri net. In this paper, we propose a new place-based refinement techinique of Petri net for automatic assembly procedure. In the proposed method, we assign some attributes to places and set the input-output relationships of transitions which connect the place-attribute combinations. The places can be divided into groups according to their attributes and we should take into account only transitions between these groups. This leads to that we can refine the Petri net easily comparing with the usual transition-based technique.
