A laser diode driving apparatus comprising an oscillator (11) for
generating a high-frequency signal; an amplifier (12) for amplifying the
high-frequency signal and outputting the amplified high-frequency signal;
current mirror circuits (7, 8 and 9) for receiving the output current of
the amplifier (12) and driving multiple laser diodes (1, 2 and 3),
respectively; a DC current supply source (10) for supplying a DC current
to the current mirror circuits, wherein the laser diode is driven using a
current obtained by superimposing the high-frequency signal on the DC
current, the laser diode driving apparatus further comprising a
high-frequency signal superimposed amplitude setting circuit (14) for
changing the amplitude of the amplifier so as to be suited for the
selection of the current mirror circuit.