PURPOSE: To detect a hot-carrier generation point precisely using an LSI tester, by transmitting a timing signal for picking up a fine luminous fail-point image to an image input unit while a testing signal is repeated from a first point to a fail point.

CONSTITUTION: An LSI tester 200 detects a fail point(FP) as a different point between an expected output value 520 estimated from a testing signal of a normal semiconductor device 500 and an observed output value 510 of a semiconductor device 500 to be measured. While a testing signal 221 is repeated from a first point to the fail point(FP), an image timing signal 130 is transmitted to a photon-counting camera head 120 at an imaging input unit 100 so that a very small luminous image is taken only at the fail point(FP). Consequently, a hot-carrier generation point can be detected for a short time without holding the testing signal 221.