The power supply device with multiple outputs includes two output ports, a power converting module with two power output ends, and two switching modules connected among the two power output ends and the two output ports. The output power from the two power output ends can be independently allocated to either one or two of the two second output ports. When one of the output ports requests for a demand power, the power supply device is able to determine which one or both of the power output ends to output power to the output port, reaching a better power allocation efficiency.