An overcurrent protection device for a power supply device includes a receiving end for receiving a current sensing signal, a compensating current unit coupled to the receiving end for compensating the current sensing signal in order to generate a current sense compensation signal, a first reference voltage generator for generating a first reference voltage, a comparator coupled between the compensating current unit and the first reference voltage generator for comparing the current sense compensation signal with the first reference voltage in order to generate a comparison result, a control unit coupled to the comparator for controlling a power switch of the power supply device according to the comparison result.