PURPOSE: To easily designate an effective keyword by sorting keywords included in data of the check result to present them to a user as a list.

CONSTITUTION: The keyword designated by the user is read in from an input part 1, and a retrieval part 2 retrieves a data base 5 based on this keyword, and the retrieval result is directly displayed on an output part 4 or is temporarily sent to a control part 3 and is displayed on the output part 4 together with a keyword list after generation of the keyword list. That is, the keyword and its frequency in use are indicated when narrowing-down is necessary. Consequently, the user easily discriminates whether the keyword is adapted to his objective information or not, and he properly designates it if it is adapted.