PURPOSE: To save labor costs by automatizing the registering operation of a keyword, and shortening a time required for the registering operation of the keyword.

CONSTITUTION: A mark is put on an important part (point) in a document with a fluorescent pen by a person who is familiar with a task at the time of registering the document for operating an image file. Then, at the time of operating the registering processing of the document (step 11) by using an image reader, an image reading is operated, whether or not the part on which the mark is put with the fluorescent felt pen exists in the document is judged (step 12). Then, when the part on which the mark is put exists, the character reading of the part is operated (step 13), the part is resolved into words, the words are registered in an index part as the keywords (step 15).