Most popular method for measuring a refractive index of an ancient glass bead is the Becke line method. However, this method is not always available for all valuable beads, because we must break the bead a little to take a small piece from it. The method developed here uses a laser. A bead was immersed in oil with a refractive index slightly different from the bead. Then a laser beam was applied to the bead and the angle of deviation due to the difference in refractive indices between the bead and the oil was measured. The same procedure was applied successively by changing the oil. The refractive index of the bead was calculated by plotting these results on coordinates of angle of deviation-refractive index of the immersion oils. This method is completely non-destructive and has a satisfying precision. Many ancient glass and translucent stone beads in Japan are now examined by this method.