in a nondestructive testing apparatus for testing normality of a blade root in a steam turbine installed in a nuclear plant or a thermal plant , an ultrasonic probe and an encoder can be mounted at the outside by only removing a casing of the steam turbine , without the necessity of withdrawing a turbine rotor , so that an automatic testing can be performed by rotating the steam turbine . since the testing result can be digitally stored , reliability of the testing is improved . furthermore , size of the testing apparatus is highly reduced for a tester to conveniently carry and install the testing apparatus alone . as a result , installation time and the whole testing time can be minimized .