Abstract: In an automatic routing/designing process of an LSI using a maze algorithm, multiple sub-regions, formed by getting a grid column partitioned by a component placed in a routing region, are extracted. And grid point availability, representing the number of grid points available for routing, is obtained for each of these sub-regions. Also, if there is any open net, then the component is vertically moved upward by one grid unit, for example, to make the net routable. If the grid point availability of a sub-region, used for routing another net, has become negative as a result of the movement of the component, then the net is rerouted to pass other sub-regions. Accordingly, even if a height constraint, for example, has been imposed on the routing region, all of the nets can be routed successfully with the constraint satisfied without increasing the number of grid points in the column direction. As a result, the number of open nets can be minimized and all of the nets are much more likely to be routed successfully.