PURPOSE: To obtain the magneto-optical recording disk supporting the amorphous layer of rare earth transition metal on a transparent polycarbonate substrate.

CONSTITUTION: The disk has a polymer layer 4 between the polycarbonate substrate 1 and the amorphous layer 2, and the absolute value of the index of double refractivity (Δnd) of the polycarbonate substrate 1 is ≤25nm when measured at room temp. by the He-Ne laser of 632.8nm wavelength, and the C/N ratio of the magneto-optical recording disk is ≥29dB. Therefore, the magneto-optical disk using the plastic substrate which is equal to or more than the inorg. material substrate such as glass in magneto-optical characteristic and excellent in handling and in mass production is obtained.