Abstract: The present invention makes it possible to represent or synthesize any odor by separating the odor into a combination of a relatively small number of odors, similarly to separating a color into three primary colors. Since the “primary odors” corresponding to the primary colors have not yet been ascertained, the present invention provides a feasible method and apparatus in which, instead of presetting such fixed primary odors, the separation, synthesis, and the like can be performed by selecting a subset of odors from among a set consisting of a plurality of odors which subset or odors enables approximation of other odors as much as possible by mixture.