A circuit testing apparatus for testing a device under test is disclosed. The circuit testing apparatus includes a function generator, a signal measuring module and a determining module. The function generator is coupled to the device under test for providing a plurality of testing signals according to a predetermined manner. The signal measuring module is coupled to the device under test and the function module for measuring a plurality of measuring signals generated by the device under test according to the plurality of testing signals and generating a plurality of measuring results according to the predetermined manner. The determining module is coupled to the signal measuring module for determining a testing result for the device under test according to the plurality of measuring results.