An error rate measuring apparatus detects a bit error of input data returned from a device under test with transmission of a test signal at an error detector, and includes a log recording unit that records log data of state transition of each lane by handshakes of a plurality of lanes in a predetermined communication standard with respect to the device under test in making the device under test transit to a state of LOOPBACK, and a display unit that displays the recorded log data of the state transition of each lane in a time-series order.