PURPOSE: To make it possible to continue retrieval processing after the end of substitution by controlling processing whether retrieval is to be continued after substitution based upon the 1st instruction or a succeeding retrieving character string is to be retrieved based upon the 2nd instruction without executing substitution.

CONSTITUTION: When retrieval is specified by means of a keyboard 8 or a pointing device 9, retrieval processing is accessed, character strings are retrieved from a cursor position on an edited document, and when the same character string as that inputted to a retrieving character string input area exists, the retrieved character string is inversely displayed. When substitution is specified after the end of retrieval, substitution processing is accessed, a substituting character string shown in a substituting character string area is substituted for the inverted display character string. When retrieval is furthermore specified after the end of retrieval, unnecessary substitution is skipped by accessing the retrieval processing. When substitution/retrieval is specified, substitution/retrieval processing is accessed, a substituting character string stored in the substituting character string area is substituted for an inverted display character string, the succeeding retrieving character string is retrieved and then its inverted display is executed.