PURPOSE: To eliminate the need for preparing a large number of substrates and the trouble for replacing chips to easily perform the test of an IC memory chip by a method wherein a large number of IC memory chips on a substrate can be independently operated by manipulating a change-over switch.

CONSTITUTION: A change-over switch SW1 is operated according to the type of IC memory chips IC1-IC4. For example, with a 1M memory capacity, the switch SW1 1-2 is turned ON; while it is 512K-bit, the 2-3 is turned ON. By connecting output signals Y0-Y3 from a decoder IC5 respectively to CE terminals of the IC memory chips IC1-IC4, i.e., by operating a change-over switch DIP1, any of the IC memory chips IC1-IC4 to be operated can be selectively controlled. In this case, since the IC memory chip to be selected can be controlled by changing over the DIP1 3-6 and 4-5, the IC memory chips IC1-IC4 can be independently selected.