The present invention relates to a net/wiring selection method for selecting, from among nets/wirings wired on the basis of layout information, a net/wiring whose layout is to be changed with priority in order to improve a delay. To enable efficient elimination of a critical path, the method is arranged to include a wiring capacitance lower limit computation step for computing wiring capacitance lower limits on the basis of layout information; an inter-wiring capacitance computation step for computing, as an inter-wiring capacitance, a difference between a real wiring capacitance and the wiring capacitance lower limit; a parallel wiring length extraction step for extracting a parallel wiring length existing between adjacent wirings of the respective wirings; and a selection step for selecting a net/wiring whose layout is to be changed, on the basis of the inter-wiring capacitance, the parallel wiring length, and a slack value.