A laser diode driver, and driving method, for driving a laser diode in an optical recording/reproducing apparatus, having an auto laser power control (APC) operation, an optical pickup device, and an optical recording/reproducing apparatus, and method therefore, using the laser diode driver. The laser diode driver includes a multiplexer, a pulse generator, a differential amplifier, and an adder. The multiplexer selectively outputs drive potentials, such as a peak power drive potential, a bias power drive potential, a read power drive potential, and the like, corresponding to power levels of a laser signal, in response to a select signal applied to the multiflexer. The pulse generator generates the select signal applied to the multiplexer, the differential amplifier calculates a difference between a monitor signal provided from a monitor diode for monitoring the laser signal output from the laser diode and a drive potential selected by the multiplexer, the adder adds an output of the differential amplifier and an output of the multiplexer and outputs a signal for driving the laser diode, and the laser diode driver itself performs the APC function, thereby reducing the potential of laser diode driver malfunction caused by electromagnetic interference.