An apparatus for testing a semiconductor integrated circuit has a test circuit board and an ancillary test device. The ancillary test device can test a digital circuit. The ancillary test device has test pattern memory, a test pattern signal generator, and a control section for controlling an operation for the test pattern data selected from among the plurality of test pattern data sets stored in the test pattern memory and an operation for writing the selected test pattern data into the test pattern signal generator. The ancillary test device generates a test input pattern signal on the basis of test pattern data written in the test pattern signal generator and determines a test output pattern signal output from the semiconductor integrated circuit on the basis of the test input pattern signal, thereby testing a digital circuit.