PURPOSE: To provide a parts quality information preparing method by which a large amount of parts quality information can by prepared in a short time.

CONSTITUTION: Defective detail data including the number of dissatisfactory parts and the number of defective parts for a pertinent month, are prepared by a defective information preparing processing (S-1) using a computer, and incoming and put-out data including the number of incoming parts and the number of put-out parts for the pertinent month, are prepared by an incoming and put-out information preparing processing (S-2) using the computer. Then, an acceptance inspection monthly is prepared by calculating the dissatisfactory ratio of the incoming parts and the defective ratio of the put-out parts for the pertinent month, from the defective detail data and the incoming and put-out data by an acceptance inspection monthly preparing processing (S-3) using the computer. Thus, the part quality information can be automatically prepared by a computer processing, so that a time and labor required for the preparation of the information can be sharply saved, and a large amount of part quality information can be prepared in a short time.