PURPOSE: To prolong the life of a laser diode without irradiating a magnet- optical disk with laser beams at a high output at the time of erasing data.

CONSTITUTION: This recording and reproducing device is provided with laser irradiating means 4, 5, 7 for irradiating the recording film of the magneto-optical disk 2 with the laser beams 6 so as to change its magnetic field direction and a heat ray 10 for preheating the recording film of the magneto-optical disk 2 before the irradiation of the recording film of the magneto-optical disk 2 with the laser beam 6 by the laser irradiating means 4, 5, 7. As a result, the size of the device is reduced and the life thereof is prolonged.