In a disk apparatus using a ferroelectric thin film coated on the surface of a disk as a recording medium, an electrode layer is formed on a substrate and the ferroelectric thin film is formed on the electrode layer, thereby forming a disk. A head is installed on an arm over the disk. The head has a reflector, and a microtip electrode, for creating or erasing polarization of the ferroelectric thin film. An optical system is provided over the head. The head moves towards or away from the disk depending on recorded information (polarization direction), and the movement is read by the optical system. Therefore, a low-priced disk apparatus, capable of freely recording and reproducing information semipermanently, is realized.