PURPOSE: To measure the signal propagation characteristic between LSI devices without bringing a probe into direct contact with the leads of LSIs.

CONSTITUTION: A logic LSI device 1 is provided with a test output terminal selection circuit 3, test signal input circuit 5, test function selecting signal input circuit 11, output selection circuits 7 and 8, and test signal input terminal (D). An other logic LSI device 2 is provided with a test input terminal selection circuit 10, test signal output circuit 12, input selection circuit 13, and test signal output terminal (R). Then a test signal is propagated through the terminal (D), a test output terminal A, a test input terminal A', and test signal output terminal (R) by respectively inputting the test signal, signal for selecting a test output terminal (A-N), and test function selecting signal and a signal for selecting a test input terminal (A'-N') connected to the test output terminal (A-N) and the test function selecting signal to the devices 1 and 2.