According to the present invention, in a CAD apparatus, circuit data for a circuit diagram created through circuit design processing is stored in a circuit database. Based on the circuit data stored in the circuit database, the respective logic types of components are discriminated and set for the component in the circuit data. Moreover, by adding logically transparent nets to the circuit data stored in the circuit database, DRC data dedicated to a DRC is created and stored in a DRC database. A DRC execution unit performs the DRC, by utilizing the DRC data stored in the DRC database.