PURPOSE: To improve the erasing rate of recorded signals, reduce the recording current and obtain generally flat frequency characteristics by providing a wavelength detecting means and a current switching means when data are to be recorded by a signal of a combination of signals of different wavelengths.

CONSTITUTION: In a signal processing part 1, data of a memory 3 converted into serial data via a bit converting circuit 4 and a P/S converting circuit 5 are input to a wavelength detecting circuit 6. A recording current of a recording signal of a longer wavelength is changed to be a smaller value at a current changing circuit 10 based on the detecting data of the circuit 6. Moreover, the detecting data are delayed by a delaying circuit 7 by a time when the recording signal is delayed through the process at the wavelength detecting means and thereafter. Accordingly, even a recording signal of a long wavelength is not recorded to a deep part of the recording medium. The recording signal of the long wavelength is prevented from remaining without being erased at an overwriting time. Moreover, since the recording current is made smaller as the wavelength is longer, the total value of the recording current is decreased.