It is possible to improve workability of a design work by handling electric information between one object and other objects associated with the object. A plurality of objects are inputted and electric information is inputted to the objects. Among the objects, mutually connected objects are virtually made into a single object. According to electric information in each of the objects, i.e., the virtually unified single object and the other objects excluding the virtually unified single object, objects having the common electric information are connected by straight lines. According to the straight lines, a figure connecting the objects is inputted. A condition for connecting the objects in the figure is inputted. According to the condition, circuit parts are built and signal information is set in a terminal of the circuit parts.