The present invention discloses a circuit testing apparatus for testing a device under test. The circuit testing apparatus includes a signal transformation module, a meter, and a logic tester. The signal transformation module is coupled to the device under test and transforms an analog output signal generated by the device under test into a DC signal. The meter is coupled to the signal transformation module and measures the DC signal so as to generate a digital measuring result. The logic tester is coupled to the meter and determines a test result for the device under test according to the digital measuring result.