A power supply device is provided. The power supply device includes a housing, a power converter, a controller, multiple humidity sensitive capacitors, and a feedback circuit. The housing has multiple joints. The controller controls the power converter to provide an output voltage. The humidity sensitive capacitors are respectively configured in the housing and adjacent to a corresponding joint of the joints. The humidity sensitive capacitors jointly provide a sensing capacitance value. The feedback circuit changes a gain value and a compensation bandwidth of the output voltage in response to the change of the sensing capacitance value. When the humidity of at least one of the joints increases, the sensing capacitance value is reduced, so that the gain value and the compensation bandwidth are reduced.