Magneto-optical disk device having a plurality of independently moving magneto-optical heads in the head window

A magneto-optical disk device, in which data are written and read in and from a magneto-optical disk housed in a magneto-optical disk cartridge having a head window of a predetermined shape, comprises: first and second magneto-optical heads disposed so as to locate in the head window for accessing the magneto-optical disk; a center rail disposed substantially at the center of the window head along a diameter of the magneto-optical disk; a first side rail and a second side rail which are disposed parallelly with each other on both sides of the center rail; a first carriage slidably disposed between the center rail and the first side rail, and having at least a part of the first magneto-optical head mounted thereon; first driving means for driving the first carriage along the center rail; a second carriage slidably disposed between the center rail and the second side rail, and having at least a part of the second magneto-optical head mounted thereon; and second driving means for driving the second carriage along the center rail.