A method of quickly supplying electric energy to electric vehicles and the power supply device thereof are provided. The method includes providing a rechargeable battery pack on an electric vehicle and providing a battery replacement device, a charging room and a battery storeroom in a power exchange station. The rechargeable battery pack includes a battery box and standardized standard battery units. The standard battery units are located in the battery box during operation, and are capable of being smoothly loaded into and unloaded from the battery box along the guiding rails. The rechargeable battery pack is pre-installed in the electric vehicle and the drained standard battery units within the battery box are replaced with fully-charged standard battery units upon payment when the electric vehicle in need of electric power supply is driven into the power exchanging station.