A method of diagnosis of an integrated logic circuit having function blocks, in which a test signal is supplied to the logic circuit; an input signal to and an output signal from at least one of the function blocks are detected by the use of a contactless probing device such as an electron beam probing device or laser beam probing device; simulation is carried out of a normal logic operation of the function block with the detected input signal to provide a simulated output signal; the detected and simulated output signals are compared with each other; and the function block is determined as being normal or abnormal according to the result of the comparison. When the function block includes plural logic elements, the cause of the abnormality may be traced back to a faulty function element by detecting the output of a function element by a contactless probing device, comparing the detected output with a corresponding simulated output and repeating the detection and comparison on other function elements in the function block until the comparison results in coincidence. The function element which receives the signal providing the coincidence as a result of the comparison is determined as the faulty function element.