PURPOSE: To reduce the operating load and to decrease the number of keys by enabling a document editing function to discriminate the detection of characters between 'deletion of characters' and 'retreat' according to whether a cursor is set or not on a character.

CONSTITUTION: It is decided in a character position decision processing whether a cursor is set on a character or not after the push of a specific key that deletes characters one by one. When the cursor is set on a character, this character is deleted in a character string changing process. When no character exists at the cursor position, it is checked in the character position decision processing whether or not a character exists at a position immediately adjacent to the sentence head side against the cursor position in case a character string is viewed toward the head of a sentence. If so, the relevant position is deleted in the character string changing process. Then the cursor is moved toward the head of the sentence by an extent equal to a single character. While the cursor is moved toward the sentence head by a single character when no character exists at the position immediately adjacent to the sentence head against the cursor position.