The present invention provides a method for verifying a design of a circuit board that has a wiring layer connecting components to be mounted, a power layer, and an insulating layer formed between the wiring layer and the power layer. According to this method, detection of chippings in the power layer is performed. The chipping is, for example, a gap, a slot, or a slit, and corresponds to one wiring layer and interrupts a region in which the wiring layer and the power layer are opposed to each other. When chippings are detected, a common-mode voltage expected to be caused owing to each of the chippings is computed. Subsequently, the position of the chipping and the value of the common-mode voltage caused owing to the chipping are outputted. Thus, the priorities of the chippings, to which countermeasure for suppressing radiation of electromagnetic waves should be applied, can easily be decided.