PURPOSE: To increase the apparent Kerr rotation angle in a short wavelength region by forming a MnSb oxide layer and a MnSb magnetic layer in this order along the direction of incident light.

CONSTITUTION: A MnSb oxide layer 2 is formed to have a proper thickness in the incident direction of light on a substrate 1 by sputtering MnSb oxide in an atmosphere into which oxygen is introduced. Further, a MnSb magnetic layer 3 is formed by sputtering in vacuum or in inert gas. Further, by another method, the layer 2 is formed by sputtering in vacuum or inert gas on the substrate 1 and then heat-treated in an atmosphere into which oxygen is introduced. Further, the layer 3 is formed by sputtering in vacuum or inert gas. By this method, reproducing light is reflected in many times in the oxide layer of the substrate side so that the apparent Kerr rotation angle is increased although the reflectance is decreased. To prevent decrease of the reflectance, a reflecting film such as Al may be formed on the laminated film.