PURPOSE: To easily find the trouble of a burn-in testing machine by applying an input signal from the testing machine to a reference IC and comparing its output with an output expected value generated by the burn-in testing machine.

CONSTITUTION: The testing machine 2 is equipped with an input signal generating circuit 21 which generates the test signal to be supplied to the device 11 of a checking device and an output signal generating circuit 22 which generates the output expected signal to be supplied to the comparator 12 of the checking device 1. The output expected value is the signal which should be outputted from the IC device to be inspected when this IC device supplied with the input signal operates normally. The checking device 1 is provided with said selected reference device 11, which operates with the input signal from the testing machine 2; and the reference output signal is outputted by the device 11 to the comparator 12. This reference output signal is compared with the output expected signal by the comparator 12 and a decision circuit 14 decides whether the testing machine operates normally or not.