PURPOSE: To enable the effective editing work by referring to a derivative development table prepared in advance by taking a conjugated form as a key, developing a word to be retrieved to a derivative word group, and retrieving the word to be retrieved and the derivative group.

CONSTITUTION: An input section 11 inputs a word to be retrieved and its conjugated form from the input device such as keyboard. A derivative development section 13 accepts the word to be retrieved and its conjugated form from a control section 12 and obtains the derivative group of the word to be retrieved by taking the conjugated form as a key and referring to a conjugated form development table 16, passing the information to the control section 12. A retrieval processing section 14 accepts the word to be retrieved and the derivative group from the control section 12, retrieving the character string of the word to be retrieved and the derivative group from the object sentence and passing the retrieved information to the control section 12. An output section 15 accepts the retrieved information from the section 12 and displays it on an output device such as a display.