A property of connection relationship information for identifying an internal/external connection of each point is registered in a part DB 1. When the part is one basic part representing a standard configuration article, an anchor ID is registered in the part DB 1 or a product DB 2. Part group extracting unit 4 extracts parts constituting a system from a design drawing generated by drawing generating unit 3 and a group of parts connected at the connection point for each basic part assigned with the anchor ID. For each extracted part group, work instruction document generating unit 5 detects a standard configuration article having a basic part assigned with the same anchor ID as that of the basic part included in the part group, from the product DB 2, extracts a difference in part configuration between the part group in the system design drawing and the detected standard configuration article, generates information indicating the extracted difference as the work instruction document for each part group, and outputs the work instruction document.