In a cushioning device of a press having a pneumatic cylinder for producing a blank-holding force to be applied to a blank through a cushion platen and a pressure ring, an optimum initial value of the pneumatic pressure of the pneumatic cylinder when the cushion platen is placed at a setup position lower than the lower stroke end is calculated based on die-set information relating to the pressure ring and including a predetermined optimum value of the blank-holding force, and machine information relating to the cushioning device, so that the calculated optimum initial pneumatic pressure provides the optimum blank-holding force during a pressing operation, irrespective of a volumetric increase of the pneumatic cylinder due to a movement of the cushion platen from the setup position to an operating position for the pressing operation. The pneumatic pressure is adjusted to the calculated optimum initial value when the cushion platen is located at the setup position.