The glass substrate test apparatus of the liquid crystal cell process comprises a laser unit for generating a laser beam, a beam shaper and beam collimator for shaping the laser beam emitted from the laser unit so as to have an elongated cross section and parallelizing the shaped laser beam, a photo detector for detecting an intensity of double refraction of the shaped laser beam transmitted over the whole glass substrate, a phase defector for measuring the laser double refraction detected by the photo detector and comparing the measured double refraction with a standard laser double refraction, and a polarizer arranged between the laser unit and the beam shaper or between the beam shaper and the beam collimator for polarizing the laser beam to a parallel ray.