PURPOSE: To simplify a circuit diagram generating operation by deciding whether a connection target is a bundle line or a single line by judging whether or not it is of bundle description, and performing connection processing by one command.

CONSTITUTION: A bundle description decision part 4 which decides whether or not the connection target retrieved by a drawing retrieval part 3 is of bundle description by referring to drawing information stored in a drawing information storage part 2 is provided. Also, a bundle line change part 6 which includes a means to connect the bundle line or the single line according to the decision result of the bundle description decision part 4 and changes an existing line to the bundle line based on the bundle description of a connection destination when a detecting part 5 performs the connection by the bundle line on the single line is provided at a connection part 5. Thence, it is checked whether or not the target is of bundle description when a symbol or a line exists, and the connection is performed with the bundle line when it is of bundle description, and with the single line in the case other than that. Also, when the connection with the bundle line is applied to the single line, the single line is changed to the bundle line. In such a way, the circuit diagram generating operation can be simplified.