PURPOSE: To obtain constant emission intensity regardless of the size of a duty in an emission pattern by controlling the gain of a control signal for the laser emission intensity on the basis of laser emitting data for the turning-on and off control of emission in a laser light source.

CONSTITUTION: The gain of the control signal for the laser emission intensity is controlled on the basis of the laser emitting data for the turning-on and off control of the emission in the laser light source. Namely, an information data signal to be recorded to an optical disk 1 is sent to a signal processing circuit 9 and the signal of the emission pattern, for which information data are modulated in the signal processing circuit 9, is sent to an emission driving circuit 7 and a gain control circuit 8. Here, a signal to pass through an LPF5 of an APC circuit is simultaneously inputted to the gain control circuit 8 and the signal of the emission pattern, which is modulated in the gain control circuit 8, and the signal to pass through the LPF5 are subtracted and after that, sent to the emission driving circuit 7 again. Thus, regardless of the size of the duty in the emission pattern, a laser light, for which the peak value of emission power is arranged, can be obtained.