PURPOSE: To improve efficiency for utilizing resources by letting a function part required for a processing on a host computer automatically rise up when it is necessary to preserve drawing data, and letting the function part on the host computer fall down when the required processing is completed while preparing a set drawing on a slave computer.

CONSTITUTION: According to an instruction, a CAD function part 1-5 activates a log-in function part 1-7 and after executing log-in to the operating system of the host computer, the log-in function part 1-7 activates a communication function part 1-3 and a preserved drawing retrieval function part 1-2 by using the function of an operating system 1-9 of the host computer. The CAD function part 1-5 reads a data to be preserved from a data base 1-4 for drawing preparation work, dispatches the data to a communication function part 1-6 and transfers the data to the communication function part 1-6, and the communication function part 1-3 dispatches the data to the preserved drawing retrieval function 1-2. Then, the preserved drawing retrieval function part 1-2 writes the data in a data base 1-1 for drawing preservation. Thus, efficiency can be improved for utilizing resources.