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.