to a voltage, and outputting the voltage; a reference voltage source for deciding a reproduction power of the semiconductor laser; an error amplifier for amplifying a difference between the output voltage of the current/voltage conversion circuit and the reference voltage; a current source for passing a current through the semiconductor laser; a reproduction power control system for connecting an output of the error amplifier to the current source, and controlling the reproduction power; a D/A conversion circuit for deciding a current to be passed through the semiconductor laser; a switch means for selectively switching between the output of the error amplifier and an output of the D/A conversion circuit, to make a control signal of the current source; an