PURPOSE: To automate the arrangement of a wiring operation by a method wherein, when the location of an apparatus inside a control board and wiring information are input by an input means, a duct selection means selects a duct in an optimum size on the basis of data on the number of interconnections which are computed by a number-of-interconnections operation means, for every wiring route.

CONSTITUTION: The location of an electric apparatus inside a control board and wiring information are input to an input processing part 31 for a CPU from a keyboard 22 for input and a magnetic disk 26. The CPU analyzes the specifications of the electric apparatus by a production-data analysis part 33, and the number of interconnections between large blocks and that between small blocks are computed by respective computation parts 34, 36. Computed results are stored in a main-duct selection and operation part 35 and a subduct selection and operation part 37. When all above processing operations are finishes regarding the electric apparatus, an output processing part 32 selects the size and the number of pieces of main ducts and those of subducts according to the number of interconnections to be housed, and they are displayed on a CRT and stored in the magnetic disk 26. Thereby, the arrangement of a wiring operation is automated with good efficiency.