PURPOSE: To securely detect a wire breaking position by irradiating wiring with an electron beam while a voltage is applied if a break of the wiring is detected, and detecting the quantity of generated secondary electrons.

CONSTITUTION: A signal input circuit 107 decides whether or not the wiring of an ITO(indium tin oxide) pattern is broken from whether or not a voltage is applied to a probe 110a and sends a signal to a controller 117. While the controller 117 controls an electron beam scanning circuit 105 to make the electron beam 103 scan the ITO pattern lengthwise in order from one end, a detector 104 detects the generated secondary electrons. The secondary electron signal sampled by a sampling circuit 106 is processed by the controller 117 to decide the place of the wire breaking. Consequently, the wire breaking place of the ITO pattern can securely and easily be detected.