1. An object data search apparatus comprising: a database for storing object data in association with a plurality of attribute words categorized according to sentence elements of a natural language; an input unit for receiving an input of a search criterion in the form of a sentence of the natural language; a criterion retrieval unit for analyzing the search criterion in the form of the sentence and retrieving one of a plurality of search words respectively corresponding to sentence element categories of the natural language; an object retrieval unit for searching the database using each of the search words respectively associated with the sentence element categories, and retrieving the object data associated with the attribute words that match a single search word or a plurality of search words; and an output apparatus for outputting the object data thus retrieved.