PURPOSE: An electronic thesaurus is provided to sort general words into the six large categories based on the experience of objects, and to arrange the sub-categories of the six categories in a logical hierarchical structure according to the types of thought. CONSTITUTION: The electronic thesaurus consists of a DB(200) recording the synonyms by sorting the synonyms into the three-step categories from the upper categories to sub categories by operation of experimental concepts, and a search engine(100) including a sentence/word input unit(101) clicking the blocked sentences of a document on a PC monitor or inputting a sentence by a key word to sample a desired synonym from the DB, a sentence analyzing/sorting unit(102) sorting the concept of the sentence by analyzing the input sentence, a list data search unit(103) sampling the code number of list data by searching the list corresponding to the analyzed/sorted sentence concept from the DB, an index data search unit(104) sampling the code number agreed with an index by searching the index agreed with the input sentence from the DB, a synonym data search unit(105) sampling the data of the code number having the sampled index, a synonym data output unit(106) outputting the sampled data by the synonym data search unit, and a synonym data selecting unit(107) selecting a desired sentence of the output data.