PURPOSE: To reduce the editing processing load by deciding the need for generation of the parenthesis information in the translation processing where an original sentence is analyzed and converted and reflecting the deciding result onto a target sentence.

CONSTITUTION: The parenthesis information including an input original sentence is analyzed as it is by an analysis processing means 1 and a conversion processing means 2. Then an intermediate expression of the original sentence is converted into that of a target sentence. A parenthesis generation decision processing means 3 decide the need for generation of the parenthesis information serving as the output target sentence. Finally a generation processing means 4 deletes the undesired parenthesis information and turns the intermediate expression of the target sentence into the target sentence. Thus it is possible to delete such parenthesis information that is needed only in the original sentence and not needed in the target sentence with no pre-editing operation nor after-editing operation. As a result, the editing processing load of a user can be reduced.