1. A circuit design aiding apparatus comprising: a circuit data storage that stores circuit data for each circuit diagram, the circuit data containing elements that form a circuit and links to constraints having been set; a constraint data storage that stores constraint data for each circuit diagram, the constraint data containing an element which is used in the circuit and to which a constraint is set and contents of the constraint; a circuit edit controller that edits contents of the circuit data stored in the circuit data storage and updates the circuit data so that the updated circuit data reflects the edited contents; and a constraint updater that extracts circuit data on an element having been edited from the circuit data storage, identifies constraint data related to the edited element from the constraint data storage based on a link to a constraint in the extracted circuit data, and changes contents of the identified constraint data.