PURPOSE: To reduce time and labor for diagnosis.

CONSTITUTION: First of all, the candidates of various question items are generated based on information stored in a knowledge data base so as to obtain information required for the diagnosis (A). Next, the plural question items to be actually inquired to human beings are selected out of these generated candidates of various question items (B). Then, these plural selected question items are presented to the human beings by an output device (C), and answers (information) to the respective question items are inputted by the human beings while using an input device. Afterwards, this input information is stored in the knowledge data base (D) and based on this input information, a proper diagnosed result is selected from the candidates of plural diagnosed results stored in the knowledge data base (E) and presented to the human beings by the output device. When no diagnosed result is obtained in a fifth process (e), the above-mentioned processing is repeated after returning to the beginning.