An automatic laser power control circuit comprises a laser diode package, a voltage adjusting unit and a polarity adjusting unit. The laser diode package emits laser light according to an applied voltage, and outputs an electric signal of a voltage proportional to the power of the emitted laser light. The voltage adjusting unit adjusts the voltage applied to said laser diode package based on the voltage of the electric signal outputted from said laser diode package. The polarity adjusting unit changes a polarity of the voltage of the electric signal outputted from said laser diode package so that the polarity is the same as that of the voltage applied to said laser diode package, and supplies the voltage having the changed polarity to said voltage adjusting unit. The automatic laser power control circuit provides an advantage that a monitor diode included in the laser diode package can be compatibly used regardless of its ground type.