A testing apparatus includes a first power supply unit for generating a current to be supplied to the device under test and first and second coaxial cables through which the current generated by the first power supply unit is supplied to the device under test, wherein the first power supply unit includes a current detecting unit for detecting an amount of a voltage drop when the current generated by the first power supply unit passes through a predetermined resistor and a current controlling unit for controlling the current being supplied to the device under test in response to the amount of the voltage drop detected by the current detecting unit, the first coaxial cable includes a first internal conductor for conducting the current from the first power supply unit towards the device under test and a first external conductor provided around the first internal conductor with an insulator interposed therebetween for conducting the current from the device under test towards the first power supply unit, and the second coaxial cable includes a second internal conductor for conducting the current from the device under test towards the first power supply unit and a second external conductor around the first internal conductor with an insulator interposed therebetween for conducting the current from the first power supply unit towards the device under test.