An apparatus for designing the layout of a circuit includes an acquiring unit, a determining unit, a specifying unit, an arranging unit, a modifying unit, and a routing unit. Based on net information acquired by the acquiring unit, the determining unit determines a wiring block of signal paths connecting cells connected through adjacent. The arranging unit arranges a wiring area between the cells that extends along user-specified reference points or user-specified reference segments received by the specifying unit. The modifying unit modifies the arranged wiring area and the routing unit routes the signal paths of the wiring block in the modified wiring area.