A power supply device includes a power conversion module and a power regulating module. The power conversion module is configured to convert an AC electric power into a DC electric power. The power regulating module includes a microprocessor, a voltage-dividing resistor, a constant-voltage regulator, and a constant-current regulator. The voltage-dividing resistor is electrically connected to the setting resistor and the microprocessor. The constant-voltage regulator is electrically connected to the power conversion module, the dividing resistor, and the setting resistor; The constant-current regulator is electrically connected to the power conversion module and the microprocessor. A constant voltage is coupled to the dividing resistor and the setting resistor to impress a first adjustment signal and a second adjustment signal based on the setting resistor such that a driving signal outputted from the power regulating module to the power conversion module is adjusted to yield a desired voltage and a desired current.