PURPOSE: To retreive an example sentence provided with a retreival key or the similar retreival key where main words are the retreival key by extracting the main words from a retreival sentence and retreiving an example sentence data base using the main words.

CONSTITUTION: The retreival sentence to be the object of retreival is read from an input device 130 and the main words (subject, verb and object) are extracted from the read retreival sentence to be stored in a main word extraction table 120. Then, extracted main word information is set as the retreival key and whether or not the main words identical to the retreival key are present is retreived by using the example sentence data base 100 stored with the main words and the related information. As the result of the retreival, when the main words can not be retreived, by adding the main word information different from the retreival key similar to the retreival key to the extracted retreival key as the related information, the main words similar to the retreival key are retreived by using a main word dictionary.