PURPOSE: To record ternary data on a magneto-optical recording medium constituted of a material composed of rare-earth elements and transition metals.

CONSTITUTION: An S- or N-magnetic field or no magnetic field is formed around a magneto-optical disk 50 of a material composed of rare-earth elements and transition metals by using a magnetic head 12. A current drive circuit 21 is driven so that the laser light outputted from a laser diode 31 can be more intensified when no magnetic field is formed around the disk 60 than the case where the S- or N-magnetic field is formed. Since data are expressed by the presence of uneven magnetization produced when the disk 60 becomes extremely high in temperature in addition to the binary data expressed by the direction of magnetization, ternary data can be recorded on the disk 60.