PURPOSE: To provide an economical cable bypass route using a heuristic method when a section having no empty conduit line has occurred.

CONSTITUTION: When laying a cable in the form of a loop, a laying route is sequentially selected between demand occurrence points and facility center in the order starting from the largest number of cores required at a demand occurrence point (Step 100). And if a section having no empty conduit line for cable laying has occurred (Step 110), another laying route bypassing the section is pursued (Step 120). Then, the costs of all the laying routes housing the number of cores of cable capable of housing the demands with the shortest path between the facility center and the demand occurrence point with the largest number of cores required are compared each other (Step 130), and a laying route with the smallest cost is extracted and the form of laying is set (Step 140).