A magnetic disk device performs magnetic recording by generating a magnetic field using an electric current on a light-irradiated surface of a recording medium. A head unit is formed by laminating an optical film that transmits a light and a metal film through which the electric current flows. A light exposing unit irradiates the light in such a manner that the light is transmitted through the optical film and irradiated on a surface of the recording medium. An electric-current output unit outputs the electric current to the metal film.