Abstract: An IC testing apparatus performs testing on a test device such as an IC using test signals each consisting of test pulses. The apparatus contains skew adjusting circuits, drivers and comparators. Herein, the skew adjusting circuit receives a test signal to perform a skew adjustment. The driver converts an output of the skew adjusting circuit in voltage to match with the test device, so that an output signal of the driver is sent to the test device for the testing. The comparator compares an input signal thereof given from the test device with a reference value. Due to the provision of the drivers and comparators, there is the driver skew and comparator skew. A decision circuit is provided to make a decision as to whether the output of the skew adjusting circuit delays or advances from a decision strobe signal which synchronizes with the test signal, thus producing a decision signal. An amount of skew corrections is counted from the decision signal with a precision to create skew correction data.