IT IS INTENDED TO PROVIDE A METHOD AND AN APPARATUS FOR LEVELING POWER OUTPUT OF A WIND TURBINE GENERATOR FACILITY AS WELL AS INCREASING POWER OUTPUT. THE POWER OUTPUT LEVELING APPARATUS 4 INCLUDES A WIND TURBINE CONTROLLER 20 FOR CONTROLLING OUTPUT OF A WIND TURBINE GENERATOR 2, A BATTERY CONTROLLER 30 FOR CONTROLLING AN ELECTRICAL STORAGE DEVICE 3, AND A MASTER CONTROLLER 40 FOR SENDING COMMANDS TO THE WIND TURBINE CONTROLLER 20 AND THE BATTERY CONTROLLER 30 RESPECTIVELY. THE OUTPUT OF THE WIND TURBINE GENERATOR 2 IS LEVELED BY THE POWER OUTPUT LEVELING APPARATUS 4 TO BE ADJUSTED TO THE TARGET OUTPUT.