A power generating device and a power supplying method thereof are provided. The power generating device includes a battery set, a charge storage device, a charger and a voltage converter. The battery set has microbial fuel cell and/or solar battery, and is used for generating a supply voltage. The charger generates a charging voltage according to the supply voltage, and provides the charging voltage through a first resistor to charge the charge storage device. The voltage converter converts a storage voltage provided by the charge storage device to generate a driving voltage, and provides the driving voltage, to drive a load. |