PURPOSE: To prevent distortion and irregular reflection at writing and to attain an optical memory not requiring an analyzer for reading, by coating an amorphous dielectric film on the surface of a substrate, irradiating laser light on the film surface and changing the transmission rate of light through the change in the irradiating point.

CONSTITUTION: An amorphous dielectric film 10 such as lead titanate is vapor- deposited on the surface of a substrate 11 with a reactive sputtering method. Laser light 13 is irradiated on a surface 12 to modify an irradiated point 14 and information is recorded by changing the transmission rate of light. Further, an optical reflection film 15 is provided with the thin film vapor-deposition of Al between the substrate 11 and the film 10 to attain light interference with the film 10 for greater contrast, allowing to read the information effectively. In this optical memory, laser light 17 from a light source 16 is irradiated on the surface of the film 10 via a lens 18 and a half mirror 19 to read a reflected light 7 at a detection section 19. Thus, writing/reading can be done effectively with a simple device.