Abstract: A propagation delay time measuring method of measuring a propagation delay time of a test signal propagating along one of a first signal path and a second signal path serially connecting to the first signal path through which a semiconductor testing apparatus includes a driver and a comparator electrically connected to a device under test, the method includes: a first connecting step of connecting an end of the first path to the driver and the comparator; a first output step of outputting a test signal from the driver to the first path; a first reflect signal receiving step of receiving a test signal at the comparator, defined as a first reflect signal, reflected at another end of the first path; a first timing detecting step of detecting a timing, defined as a first timing; a second connecting step of connecting an end of the second path to another end of the first path; a second output step of outputting the test signal from the driver to the second path; a second reflect signal receiving step of receiving