To provide a clearance check method to suppress any cross-talk noises between copper foil patterns including not only between same layers but also between dissimilar layers.

The copper foil pattern in which a current of a high-speed digital signal of a frequency higher than a predetermined value runs is extracted as an element to be inspected (#102), and the copper foil pattern for a signal in proximity to the element to be inspected in the same copper foil layer as the element to be inspected and the copper foil pattern for signal in proximity to the element to be inspected in the copper foil layer dissimilar from the element to be inspected are extracted as proximity elements, and the minimum distance between the element to be inspected and the proximity elements is obtained (#103). If the minimum distance is smaller than the preset violation distance, the length of the copper foil pattern of the element to be inspected or the proximity elements included in a range in which the distance between the element to be inspected and the proximity element is shorter than the violation distance is obtained as the proximity pattern length (#105), and if the proximity pattern length is larger than the present violation length, the proximity pattern length is detected as a clearance violation (#106 and #107).