An object of the present invention is to shorten the scan time of the circuit board. Mounting table 13, the source signal line of the substrate member 12 is placed above, via the terminal from the signal supplying means 17, the frame 14 is applied to the high-frequency signal. In the scanning wiring of the substrate member 12, the absolute value of the voltage is greater than the voltage amplitude of the high-frequency signal, the voltage polarity is applied to the signal positive. Picks up an infrared image of a signal applied to the state the substrate member 12 in the image pick-up means 15. In the image processing means (16), forming an infrared image obtained by the contrast changes according to the amount of infrared radiation from the image data provided from chwalseong means 15, it divides the infrared image in a plurality of areas of an equal size, the wiring pattern. The control means 18 detects the different points as compared with the image of a plurality of adjacent images of the divided regions, each region. When the top point detecting that region, it is determined to be defective.