A test device for a system-on-chip includes a sequential logic circuit and a test circuit. The sequential logic circuit generates a test input signal by converting a serial input signal into a parallel format in response to a serial clock signal and a serial enable signal and generates a serial output signal by converting a test output signal into a serial format in response to the serial clock signal and the serial enable signal. The test circuit includes at least one delay unit that is separated from a logic circuit performing original functions of the system-on-chip, performs a delay test on the at least one delay unit using the test input signal in response to a system clock signal and a test enable signal, and provides the test output signal to the sequential logic circuit, where the test output signal representing a result of the delay test.