Abstract: A program power supply of a tester applies a power supply voltage to an IC to be tested. A pattern generator applies a clock signal and a command signal to a BIST circuit of IC. BIST circuit tests memory IC unit and logic IC unit and serially outputs data indicative of test result to a converter of tester. Converter converts the applied serial data to parallel data and applies to computer. As compared with the prior art in which address signal and control signal are applied to IC to be tested, the number of pins necessary for the test can be reduced. Therefore, cost of the test is reduced and efficiency of the test is improved.