To improve operability and productivity by updating net information covering a plurality of pages at any time when a circuit diagram consisting of plural pages is generated and edited.

This editor has a circuit diagram editor execution part 2 which generates and edits a circuit diagram, a circuit diagram data structure 6 which holds circuit information being generated and edited, and inter-page net information 7 displaying inter-page connection information on an inter-page net. Thus, a function for displaying the net information covering a plurality of pages on a screen is available, so name misaddition to an inter-page terminal is reduced by editing the diagram while confirming the connection destination of the inter-page terminal to improve the productivity. Further, the said net information is displayed on the screen and the page of the connection destination can be displayed with the information, so the connection destination of an arbitrary inter-page terminal is displayed and the page of the connection destination is immediately displayed for editing operation to be advanced, thereby improving the operability.