A test interface device includes a serializer, an optical transmitter, an optical receiver, and a deserializer. The serializer receives parallel test signals from automatic test equipment, and serializes the parallel test signals into a serial test signal. The optical transmitter converts the serial test signal into an optical test signal. The optical receiver receives the optical test signal from the optical transmitter, and converts the optical test signal into the serial test signal. The deserializer deserializes the serial test signal into the parallel test signals, and transmits the parallel test signals to a device under test. As a result, signal transfer speed may be improved and optical resource usage may be reduced.