The optical axis orientation measuring device according to the present invention is a reflective optical axis orientation measuring device for a spherical member made from a single crystal of an optically uniaxial crystal having birefringence, comprising: illuminating means for illuminating the spherical member through a polarizer; and isogyre observing means for observing the isogyre that is structured by the light that is reflected from the bottom surface of the spherical member and emitted from the spherical member through an analyzer that has a cross-nicol relationship with the polarizer.
